Nuclear weapons and the United Kingdom

The United Kingdom was the third country to test an independently developed nuclear weapon, in October 1952. It is one of the five nuclear-weapon states under the NPT and a permanent member of the UN Security Council.

The UK is thought to retain a stockpile of around 225 thermonuclear warheads, of which 160 are operational, but has refused to declare the exact size of its arsenal. Since 1998, the Trident programme has been the only operational nuclear weapons system in British service.

The delivery system consists of four Vanguard class submarines based at HMNB Clyde in Scotland. Each submarine is armed with up to 16 Trident II missiles, each carrying warheads in up to eight MIRV re-entry vehicles. With at least one submarine always on patrol, the Vanguards perform a strategic deterrence role and are also believed to have a sub-strategic capability.

Since the 1958 US-UK Mutual Defence Agreement, the United States and the United Kingdom have cooperated extensively on nuclear security matters. The special relationship between the two countries has involved the exchange of classified scientific data and materials such as plutonium.

The UK has not run a programme to develop an independent delivery system since the cancellation of the Blue Streak missile in 1960. Instead it has purchased US delivery systems for UK use, fitting them with warheads designed and manufactured by the UK's Atomic Weapons Establishment and its predecessor. In 1974, a US proliferation report discussing British nuclear and missile development noted that "In many cases, it is based on technology received from the US and could not legitimately be passed on without US permission."

In contrast with the other permanent members of the United Nations Security Council, the United Kingdom operates only a submarine-based delivery system, having decommissioned its tactical WE.177 free-fall bombs in 1998.

The Atomic Weapons Establishment is undertaking research which is largely dedicated to providing new warheads and on 4 December 2006 the then Prime Minister Tony Blair announced plans for a new class of nuclear missile submarines.

Number of warheads
Since 1969 the United Kingdom has always had at least one ballistic-missile submarine on patrol, giving it a nuclear deterrent that is what the Defence Council described in 1980 as "effectively invulnerable to pre-emptive attack". In the Strategic Defence Review published in July 1998, the government stated that once the Vanguard submarines became fully operational (the fourth and final one, Vengeance, entered service on 27 November 1999), it would "maintain a stockpile of fewer than 200 operationally available warheads". The Stockholm International Peace Research Institute has estimated the figure as about 165, consisting of 144 deployed weapons plus an extra 15 percent as spares.

At the same time, the UK government indicated that warheads "required to provide a necessary processing margin and for technical surveillance purposes" were not included in the "fewer than 200" figure. As recently declassified archived documents on Chevaline make clear, the 15% excess (referred to by SIPRI as for spares) is normally intended to provide the 'necessary processing margin', and 'surveillance rounds do not contain any nuclear material, being completely inert. These surveillance rounds are used to monitor deterioration in the many non-nuclear components of the warhead, and are best compared with inert training rounds. The SIPRI figures correspond accurately with the official announcements and are likely to be the most accurate. The Natural Resources Defense Council speculates that a figure of 200 is accurate to within a few tens. In 2008 the National Audit Office stated that the UK stockpile was of fewer than 160 operationally available nuclear warheads. During a debate on the Queen's Speech on 26 May 2010 Foreign Secretary William Hague reiterated that the UK has no more than 160 operationally available warheads, and announced that the total number will not exceed 225.

Historical
Until the 1990s the UK deployed a wide variety of nuclear weapons around the world, such as V bombers in Singapore in the 1960s, aircraft on Cyprus and on Royal Navy carriers in the 1960s and 1970s, and four ships in the fleet sent to the South Atlantic during the 1982 Falklands War. Until August 1998, the UK retained the WE.177 nuclear weapon manufactured in the mid-1960s to late 1970s, in air-dropped free-fall bomb and depth charge versions. Its withdrawal left the four Vanguard class submarines, which replaced the Polaris ones in the early 1990s, as Britain's only nuclear weapons platform. It has been estimated by the Bulletin of the Atomic Scientists that the United Kingdom has built around 1,200 warheads since the first Hurricane device of 1952. In terms of number of warheads, the UK arsenal was at its maximum size of about 520 in the 1970s, but this figure does not include the large numbers of US-owned warheads, bombs, nuclear depth bombs supplied from US stocks in Europe for use by NATO allies. At its peak, these numbered 327 for the British Army of the Rhine in Germany alone.

Weapons tests
The United Kingdom tested its first nuclear weapons in Australia during the 1950s, on the Montebello Islands (Western Australia) and at the Woomera Prohibited Area (South Australia).

The first detonation, codenamed Operation Hurricane, occurred on 3 October 1952, in a shallow bay on Trimouille Island. Two further tests were held on the Montebello Islands during 1956. The second of these, codenamed "G2", included the largest nuclear explosion in Australia, with a yield of 98 kilotons. Seven further nuclear tests were conducted on the Australian mainland between 1955 and 1963, within the Woomera Prohibited Area, at Emu Field and Maralinga in South Australia.

The first British hydrogen bombs were tested during Operation Grapple at Malden Island and Christmas Island in the Central Pacific Ocean. The operation consisted of nine tests in the period 1957–1959, ultimately proving that the UK had developed thermonuclear weapons.

Different sources give the total number of test explosions that the UK has conducted as either 44 or 45. The 24 tests from December 1962 onwards were in conjunction with the United States at the Nevada Test Site with the final test being the Julin Bristol shot which took place on 26 November 1991.

Because Britain did not test as often as the United States due to financial and political reasons, and did not have the Americans' state-of-the-art computer facilities, British weapons design depended more on theoretical understanding, with potential for both greater advances and risks between tests. The low numbers of UK tests is misleading when compared to the large numbers of tests carried out by the US, the Soviet Union, China, and especially France; because the UK has had extensive access to US test data, obviating the need for UK tests: and an added factor is that many tests required are for 'weapon effects tests'; tests not of the nuclear device itself, but of the nuclear effects on hardened components designed to resist ABM attack. Numerous such 'effects' tests were done in support of the Chevaline programme especially; and there is some evidence that some were permitted for the French programme to harden their RVs and warheads; because most French tests being under the ocean floor, access to measure 'weapon effects' was nigh impossible. An independent test programme would see the UK numbers soar to French levels.

The UK government signed the Partial Test Ban Treaty on 5 August 1963 along with the United States and the Soviet Union which effectively restricted it to underground nuclear tests by outlawing testing in the atmosphere, underwater, or in outer space. The UK signed the Comprehensive Test Ban Treaty on 24 September 1996 and ratified it on 6 April 1998, having passed the necessary legislation on 18 March 1998 as the Nuclear Explosions (Prohibition and Inspections) Act 1998.

Warning systems


The UK has relied on the Ballistic Missile Early Warning System (BMEWS) and, in later years, Defense Support Program (DSP) satellites for warning of a nuclear attack. Both of these systems are owned and controlled by the United States, although the UK has joint control over UK based systems. One of the four component radars for the BMEWS is based at RAF Fylingdales in North Yorkshire.

In 2003 the UK government stated that it will consent to a request from the US to upgrade the radar at Fylingdales for use in the US National Missile Defense system.

Nevertheless, missile defence is not currently a significant political issue within the UK. The ballistic missile threat is perceived to be less severe, and consequently less of a priority, than other threats to its security.

Attack scenarios
During the Cold War, a significant effort by government and academia was made to assess the effects of a nuclear attack on the UK. There were four major exercises:


 * Exercise Inside Right took place on 6–26 October 1975.
 * Exercise Scrum Half conducted in 1978.
 * Exercise Square Leg conducted in 1980. The scenario involved around 130 warheads with a total yield of 205 megatons (69 ground burst, 62 air burst) with an average of 1.5 megatons per bomb. The exercise was criticised as unrealistic as an actual exchange would be much larger, with one academic describing a 200-megaton attack as an "extremely low figure and one which we find very difficult to take seriously", and did not include targets in Inner London such as Whitehall. Even so, the effect of the limited attack in Square Leg was estimated to be 29 million dead (53% of the population) and 6.4 million seriously injured.
 * Exercise Hard Rock planned for 1982. A combined communications and civil defence exercise planned for September and October 1982. It assumed a conventional war in Europe lasting 2–3 days, during which the United Kingdom would be attacked with conventional weapons, then a limited nuclear exchange with 54 warheads being used against military targets in the UK. 250,000 people protested against the exercise and 24 councils refused to participate. The limited scenario still assumed casualties of 7.9 million dead and 5 million injured. The scenario was ridiculed by the Campaign for Nuclear Disarmament and the exercise was postponed indefinitely. The New Statesman later claimed the Ministry of Defence insisted on having a veto over proposed targets in the exercise and several were removed to make them politically more acceptable, for example the nuclear submarine base HMNB Clyde was removed from the target list.

In the early 1980s it was thought an attack causing almost complete loss of life could be achieved with the use of less than 15% of the total nuclear yield available to the Soviets.

Civil defence
During the cold war, various governments developed civil defence programmes aimed to prepare civilian and local government infrastructure for a nuclear strike on the UK. A series of seven Civil Defence Bulletin films were produced in 1964; and in the 1980s the most famous such programme was probably the series of booklets and public information films entitled Protect and Survive.

"If the country was ever faced with an immediate threat of nuclear threat or complete annihilation, a copy of this booklet would be distributed to every household as part of a public information campaign which would include announcements on television and radio and in the press. The booklet has been designed for free and general distribution in that event. It is being placed on sale now for those who wish to know what they would be advised to do at such a time."

The booklet contained information on building a nuclear refuge within a so-called 'fall out room' at home, sanitation, limiting fire hazards and descriptions of the audio signals for attack warning, fallout warning and all clear. It was anticipated that families might need to stay within the fall-out room for up to fourteen days after an attack almost without leaving it at all.

The government also prepared a recorded announcement which was to have been broadcast by the BBC if a nuclear attack ever did occur.

Sirens left over from the London Blitz during World War II were also to be used to warn the public. The system was mostly dismantled in 1993.

Weapons programmes
See also History of nuclear weapons

Tube Alloys and Manhattan Project
The United Kingdom's nuclear weapons had their genesis in the Second World War when two recently exiled atomic scientists, Otto Frisch and Rudolf Peierls wrote a memorandum on the construction of "a radioactive super-bomb". Forwarded to the Ministry of Aircraft Production (MAP), the secret MAUD Committee to evaluate the possibilities was soon set up. British scientists worked initially alone on the atomic bomb under the cover name of Tube Alloys, later becoming a partner in the tri-national Manhattan Project under the Quebec Agreement. The Manhattan Project resulted in the two nuclear weapons dropped over Japan.

End of American cooperation
After Hiroshima and Nagasaki revealed the existence of the atomic bomb to the world, Labour Prime Minister Clement Attlee published a detailed account, prepared by his Conservative predecessor Winston Churchill, of the United Kingdom's participation in developing the bomb. On 8 August 1945 Attlee sent a message to President Harry Truman in which he referred to themselves as "heads of the Governments which have control of this great force". For the next year he attempted to persuade Truman to grant access to information which the British believed they deserved given their involvement.

The Americans disagreed. Manhattan Project head Leslie Groves had excluded British scientists from participating in the manufacturing of the Hiroshima and Nagasaki bombs, contrary to the intentions of his government for close cooperation, for security reasons. Postwar spy scandals in both countries increased American concerns over atomic secrecy. More importantly, Truman hoped to establish international control over atomic weapons, and sharing information with even a close ally like Britain might have made such controls impossible. Nonetheless, the Americans' refusal to share information, formalised by the McMahon Act of 1946 restricting foreign access to US nuclear technology, shocked and disappointed the British.

Resumption of independent UK efforts
The United Kingdom started independently developing nuclear weapons again shortly after the war. Attlee set up a cabinet sub-committee, the Gen 75 Committee (GEN.75) (known informally as the "Atomic Bomb Committee"), to examine the feasibility as early as 29 August 1945. A September 1945 study forecast that an enemy could build 500 bombs during "ten years of 'peace'", and warned that if 10% of the arsenal was used on the United Kingdom "over night the main base of the British Empire could be rendered ineffective", with enough left for other British forces around the world. The Chief of the Air Staff Arthur Tedder officially requested an atomic weapon in August 1946, but work on a British equivalent to the vast American facilities at Hanford, Washington and Oak Ridge, Tennessee began in February 1946. American refusal to continue nuclear cooperation (except in certain non weapons-related areas in exchange for uranium from the British-controlled supply in the Belgian Congo) only affected the amount of cooperation the British expected to receive, for the government had decided that atomic weapons were vital to the nation regardless of cost:

"In October 1946, Attlee called a small cabinet sub-committee meeting to discuss building a gaseous diffusion plant to enrich uranium. The meeting was about to decide against it on grounds of cost, when [Ernest] Bevin arrived late and said "We've got to have this thing. I don't mind it for myself, but I don't want any other Foreign Secretary of this country to be talked at or to by the Secretary of State of the US as I have just been... We've got to have this thing over here, whatever it costs ... We've got to have the bloody Union Jack on top of it.""

The committee, under pressure from Hugh Dalton and Sir Stafford Cripps to opt out of building the bomb due to its cost, eventually decided to go ahead because of the likely industrial importance of atomic energy and to increase Britain's prestige and influence. The nation's leaders wished for close cooperation with the Americans but was unsure whether it would continue. Bevin believed that Britain and Europe could, with help from the Commonwealth, become an independent "Third Force" equal to the United States and the Soviet Union. Military leaders disagreed, seeing an American partnership as the only way for Britain to resist the Soviets. It is likely that covert communications between the two nations' militaries on nuclear issues, unknown to and sometimes contradicting civilian leaders' wishes, began at this time.

A nuclear programme started in 1946 under the control of the Atomic Energy Research Establishment (incorporated into the United Kingdom Atomic Energy Authority (UKAEA) in 1954), that was civilian in character, but was also tasked with the job of producing the fissile material, initially only plutonium 239, that was expected to be required for a military programme. It was based on a former airfield, Harwell, Berkshire; and a former Royal Ordnance Factory, Risley in Cheshire. Risley became the headquarters of the Industrial Division of UKAEA, and there were other sites under its control, notably the Calder Hall reactors at Windscale (later Sellafield) used to produce weapons grade Pu-239. The first nuclear pile in the UK, GLEEP, went critical at Harwell on 15 August 1947. The first plutonium metal was ready at Windscale in March 1952. AWRE was established at Aldermaston by the Ministry of Supply; later becoming the Weapons Division of the (civilian) UKAEA, before being subsumed into the Ministry of Defence in the 1970s.

William Penney, a physicist specialising in hydrodynamics was asked in October 1946 to prepare a report on the viability of building a UK weapon. Joining the Manhattan project in 1944, he had been in the observation plane Big Stink over Nagasaki, and had also done damage assessment on the ground following Japan's surrender. He had subsequently participated in the American Operation Crossroads test at Bikini Atoll. As a result of his report, the decision to proceed was formally made on 8 January 1947 at a meeting of the GEN.163 committee of six cabinet members including Attlee, with Penney appointed to take charge of the programme.

The project was hidden under the code-name High Explosive Research or HER and was based initially at the Ministry of Supply's Armament Research and Development Establishment (ARDE) at Fort Halstead in Kent, and also at the Royal Arsenal, Woolwich. In 1951 it moved to a new site at AWRE Aldermaston in Berkshire. The Attlee ministry revealed the existence of a British atomic program in Parliament on 12 May 1948; the announcement was viewed by Parliament, the press, and the people as uncontroversial. However, although British scientists knew well the areas of the Manhattan Project in which they had worked they knew little of the other areas. Building a full-scale plant for production of weapons-grade U-235 would be very expensive, and the McMahon Act prevented American technical aid. The government refused to provide public details on its progress beyond stating that atomic weapons research was of the highest priority, but it was assumed that the project was following the Americans' precedents. While Leader of the Opposition, Churchill criticised the government in February 1951 for not having completed an atomic weapon.

Unsuccessful attempt to renew American partnership
By 1949, international control of atomic weapons seemed almost impossible to achieve, and Truman proposed to the Joint Committee on Atomic Energy in July a "full partnership" with Britain in exchange for uranium; negotiations between the two countries began that month. While the first Soviet atomic bomb test in August 1949 was embarrassing to the British (who had not expected a Soviet atomic weapon until 1954) for having been beaten, it was for the Americans another reason for cooperation. Although they would soon have their own nuclear capability, the British proposed that instead of building their own uranium-enrichment plant they would send most of their scientists to work in the US, as well as plutonium from Windscale. While Britain would not formally give up building or researching its own weapons, the United States would manufacture all bombs and allocate some to Britain.

By agreeing to subsume its own weapons program within the Americans', the plan would have given Britain nuclear weapons much sooner than its own target date of late 1952. Although a majority of Americans including Truman supported the proposal several key officials, including the Atomic Energy Commission's Lewis Strauss and Senator Arthur Vandenberg, did not. Their opposition, and security concerns caused by the arrest in early 1950 of Klaus Fuchs, a Soviet spy working at Harwell, ended the negotiations in January 1950. After Britain developed atomic weapons through its own efforts, the scientist Sir Leonard Owen nonetheless stated that "the McMahon Act was probably one of the best things that happened ... as it made us work and think for ourselves along independent lines."

First test and early systems
Churchill, now again prime minister, announced on 17 February 1952 that the first British weapon test would occur before the end of the year. Operation Hurricane was detonated below the frigate HMS Plym anchored in the Monte Bello Islands, Western Australia on 3 October 1952. This led to the first deployed weapon, the Blue Danube free-fall bomb, in November 1953. It was very similar to the American Mark 4 weapon in having a 60 in diameter, 32 lens implosion system with a levitated core suspended within a natural uranium tamper. The warhead was contained within a bomb casing measuring 62 inches (1.6 m) diameter and 24 feet (7.3 m) long, and being so large, could only be carried by the V bomber fleet.

A nuclear landmine dubbed Brown Bunny, later Blue Bunny, and finally Blue Peacock that used the Blue Danube warhead was developed from 1954 with the goal of deployment in the Rhine area of Germany. The system would have been set to an eight-day timer in the case of invasion of Western Europe by the Soviets but was cancelled in February 1958 with only two built. It was judged that the risks posed by the nuclear fallout and the political aspects of preparing for destruction and contamination of allied territory were too high to justify. Another reason for cancellation revealed by numerous archived declassified documents was that the Army felt it was too unwieldy and diverted their efforts into a successor, Violet Vision, based on the smaller successor to Blue Danube, Red Beard. None were ever built, the Army instead receiving US ADMs or Atomic Demolition Munitions under the established procedures for supply of NATO allies from US stocks held in US custody in Europe. A sea mine based on the Blue Danube warhead and codenamed Cudgel was also envisaged for delivery by midget submarines, referred to by naval sources as "sneak craft"; perhaps reflecting a belief that these craft were really rather ungentlemanly methods of waging war. None were built.

A gaseous diffusion plant was built at Capenhurst, near Chester and started production in 1953 producing low enriched uranium (LEU). By 1957 it was capable of annually producing 125 kg of highly enriched uranium (HEU). The capacity was further increased and by 1959 it may have been producing as much as 1600 kg per year. At the end of 1961, having produced between 3.8 and 4.9 tonnes of HEU it was switched over to LEU production for civil use. Additional plutonium production was provided by eight electricity generating Magnox reactors at Calder Hall and Chapelcross which started operating in 1956 and 1959 respectively.

Debate
A month after Britain's first atomic weapons test, America tested the first thermonuclear (hydrogen) bomb. The Soviets tested their first in 1953. Penney believed that Britain could not afford to develop a hydrogen bomb. Henry Tizard believed that the nation should focus on conventional forces instead of duplicating the nuclear capabilities of the American Strategic Air Command, which already defended Britain and Europe. He stated:

"We are not a Great Power and never will be again. We are a great nation, but if we continue to behave like a Great Power we shall soon cease to be a great nation. Let us take warning from the fate of the Great Powers of the past and not burst ourselves with pride. (See Aesop's fable of the frog)."

First Sea Lord Lord Mountbatten and Chief of the Imperial General Staff Gerald Templer supported the development of a hydrogen bomb, but preferred more support for conventional forces. They believed that the large American and Soviet nuclear forces acted as mutual deterrents for nuclear war, making conventional war more likely. Others proposed that, instead of being frustrated by its repeated unsuccessful attempts to increase cooperation with the Americans, Britain work with Australia, Canada, and other Commonwealth countries. (Britain could not disclose atomic information to Australia despite testing weapons there because of restrictions in existing agreements with the United States.)

The Chiefs of Staff Committee and the Churchill ministry, however, believed that

"If we did not develop megaton weapons we would sacrifice immediately and in perpetuity our position as a firstclass power. We would have to rely on the whim of the United States for the effectiveness of the whole basis of our strategy."

The American alliance remained important to Britain's atomic program, despite the difficulties, because the possibility of accessing the immense American technical expertise was too valuable. The government decided on 27 July 1954 to begin development of a thermonuclear bomb and announced its plans in February 1955.

An independent deterrent
Believing that the United Kingdom was extremely vulnerable to a nuclear attack to which defence was impossible, the Chiefs of Staff and the RAF first advocated a British nuclear deterrence—not just nuclear weapons—in 1945: "[I]t is our opinion that our only chance of securing a quick decision is by launching a devastating attack upon [enemy cities] with absolute weapons." In 1947 the Chiefs of Staff stated that even with American help the United Kingdom could not prevent the "vastly superior" Soviet forces from overrunning Western Europe, from which Russia could destroy Britain with missiles without using atomic weapons. Only "the threat of large-scale damage from similar weapons" could prevent the Soviet Union from using atomic weapons in a war. John Slessor, who became Chief of the Air Staff in 1950, wrote that year that the Soviet superiority in European forces was so great that even "an ultimatum by Russia within the next two to three years" might cause Western Europe to surrender without a war. He feared that the United Kingdom might also do so "unless we can make ourselves far less defenceless than we are now." By 1952 the Air Ministry had abandoned the concept of a conventional defense of Western Europe. The hydrogen bomb increased the threat to Britain. In 1957, a government study stated that although RAF fighters would "unquestionably be able to take a heavy toll of enemy bombers, a proportion would inevitably get through. Even if it were only a dozen, they could with megaton bombs inflict widespread devastation." Although disarmament remained a British goal, "the only existing safeguard against major aggression is the power to threaten retaliation with nuclear weapons."

Churchill stated in a 1955 speech that deterrence would be "the parents of disarmament" and that, unless Britain contributed to Western deterrence with its own weapons, during a war the targets that threatened it the most might not be prioritized. Harold Macmillan stated that nuclear weapons would give Britain influence over targeting and American policy, and would affect strategy in the Middle East and Far East. Duncan Sandys stated that nuclear weapons reduced Britain's dependence on the United States. The Suez Crisis increased the value to Britain of a deterrent that would give it greater influence with the US and USSR.

Independent targeting was also vital. The Chiefs of Staff believed that—contrary to Tizard's view—once the USSR became able to attack the United States itself with nuclear weapons in the late 1950s, America might not risk its own cities to defend Europe, or not emphasize targets that endangered the United Kingdom more than the United States:

"When New York is vulnerable to attack the United States will not use her strategic weapon in defence of London. The United Kingdom must, therefore, have its own retaliatory defence. Similarly, however, we will not be prepared to sacrifice the United Kingdom in the defence of say Darwin, and eventually each political unit must have its own means of retaliation."

Britain thus needed the ability to convince the USSR that attacking Europe would be too costly regardless of American participation. Part of the perceived effectiveness of an independent deterrent was the willingness to target enemy cities. Slessor saw atomic weapons as a way to avoid a third devastating world war given that the two previous ones had begun without them. While he sought to deemphasize city targeting in British plans as Air Chief, Slessor wrote in 1954 after retirement:

"And if [war] is forced upon us, we must be able to instantly deliver a crushing counter attack upon aggression at its source—not merely at its airfields, its launching sites and submarine bases, at its armies in the field but at the heart of the aggressor country. There will be the battlefield if battlefield there must be."

When Nigel Mills became head of RAF Bomber Command in 1955 he similarly insisted on targeting Soviet cities, writing "Whoever would be afraid of launching a sudden attack if he thought the greater part of our retaliation would come back to his airfields?" The belief in the importance of retaining an independent capability has continued over several decades and changes in government. As the Defence Council stated in 1980,

"our force has to be visibly capable of making a massive strike on its own ... We need to convince Soviet leaders that even if they thought ... the US would hold back, the British force could still inflict a blow so destructive that the penalty for aggression would have proved too high."

There was little dissent in the House of Commons; nuclear weapons had almost bipartisan support until 1960, with only the Liberals dissenting in 1958. Despite opposition from its left wing the Labour party supported British nuclear weapons but opposed tests, and Labour Opposition Leader Hugh Gaitskell and shadow foreign secretary Aneurin Bevan agreed with Sandys on the importance of reducing dependence on the American deterrent. The left-wing Bevan told his colleagues that their demand for unilateral nuclear disarmament would send a future Labour government "naked into the conference chamber" during international negotiations. The Manchester Guardian and other newspapers critical of the Conservative government supported the British deterrent, although the Guardian did criticise the government for relying on developing bombers rather than missiles to carry the weapons. In 1962 it stated that the forthcoming Chinese nuclear weapon was a reason for having more than one Western nuclear nation. From 1955 the government chose to emphasize the nuclear deterrent and deemphasize conventional forces, a decision The Economist, the New Statesman, and many left-wing newspapers supported. Their view (in 1954–55) is fairly summarised as being not opposed to nuclear deterrence and nuclear weapons, but in their view that of the United States would suffice, and that of the costs of the 'nuclear umbrella' was best left to be borne by the United States alone.

Renewed American partnership
The first prototype, Short Granite, was detonated on 15 May 1957 in Operation Grapple, with disappointing results at 300 ktonTNT, when the target requirement was 1 MtonTNT. A further test of Purple Granite yielded less at 200 ktonTNT. An interim weapon was deployed in the V-bomber fleet until a true thermonuclear weapon could be devised from the Christmas Island tests. This interim weapon was never tested; it was a very large unboosted pure fission weapon estimated to yield 400 ktonTNT. It was derived from the Orange Herald warhead tested on 31 May 1957 yielding 720 ktonTNT known as Green Grass.

After British scientists demonstrated to the United States in late 1957 that they had developed a Teller-Ulam design different from American methods and thus understood how to build a hydrogen bomb, the 1958 US-UK Mutual Defence Agreement made fully developed and tested American designs available more quickly and more cheaply. The first of these was the US B28 nuclear bomb, which was anglicised and manufactured in the UK as Red Snow and quickly deployed as Yellow Sun Mk.2 in the V-bomber fleet. Red Snow became the warhead of choice for the Blue Steel stand-off missile and some of the Skybolt missiles intended for carriage by the V-bombers. (The American B28 design had reliability issues. The British soon withdrew their warheads from deployment, and never again simply copied an American design.) Under the Mutual Defence Agreement 5.4 tonnes of UK produced plutonium was sent to the US in return for 6.7 kg of tritium and 7.5 tonnes of HEU over the period 1960–1979, replacing Capenhurst production, although much of the HEU was used not for weapons, but as fuel for the growing UK fleet of nuclear submarines, both of the Polaris variety and others numbering approx twelve.

Fifty-eight Blue Danube bombs were produced, although archived declassified files indicate that only a small proportion of these were ever serviceable at any one time. It remained in service until 1963, when it was replaced by Red Beard, a smaller tactical boosted fission weapon that used the same fissile core as Blue Danube and was deployed on many smaller aircraft than the V-bombers, both ashore and at sea aboard five carriers. Stocks of Red Beard were maintained in Cyprus, Singapore, and a smaller number in the UK.

It was the largest pure fission weapon ever deployed by any nuclear state. Green Grass was deployed first in a modified Blue Danube casing and known as Violet Club. A later variant was deployed in a Yellow Sun Mk.1 casing.

In 1960 the government cancelled the Blue Streak missile based on the Chiefs of Staff's conclusion that it was too vulnerable to attack and thus was only useful for a first strike and decided to purchase the American Skybolt missile instead. In 1962 it cancelled the Blue Steel extended range upgrade (Blue Steel Mk2) for Skybolt. Similarly, reassessments of Soviet capabilities changed military perceptions and led to the removal of Thor IRBM missiles in the UK; and Jupiter IRBMs in Italy and Turkey; although the Turkish sites were implicated in an alleged deal following the Cuban Missile Crisis. To consternation, and considerable protests, the incoming Kennedy administration cancelled Skybolt at the end of 1962 because it was believed by the US Secretary of State for Defense, Robert McNamara, that other delivery systems were progressing better than expected, and a further expensive system was surplus to US requirements.

End of bipartisan support
Gaitskell's Labour party ceased supporting an independent deterrent in 1960 via its new "Policy for Peace", after the cancellation of Blue Streak made nuclear independence less likely. Labour also adopted a resolution favoring unilateral disarmament. Although Gaitskell opposed the resolution and it was reversed in 1961 in favor of continuing support of a general Western nuclear deterrent, the party's opposition to a British deterrent remained and became more prominent. This became a campaign issue during the 1964 general election. Alec Douglas-Home's incumbent Conservatives stated that the British deterrent was both necessary for independence from the Americans and maintaining British world influence, and was "working for peace" in such cases as the passage of the Nuclear Test Ban Treaty. Led by Gaitskell's successor Harold Wilson, Labour emphasized domestic economic issues but called deterrence the "Tory Nuclear Pretense" which would be neither independent nor effective. The populace's greater interest in domestic over foreign policy likely contributed to Labour's victory.



Polaris
After the cancellation of Skybolt, the UK purchased Polaris missiles for use in UK-built ballistic missile submarines. The agreement between US President John F. Kennedy and Prime Minister of the United Kingdom Harold Macmillan, the Polaris Sales Agreement, was announced on 21 December 1962 and HMS Resolution made her first Polaris-armed operational patrol on 15 June 1968. In the 1970s the UK Polaris RVs and warheads were vulnerable to the Soviet ABM screen concentrated around Moscow, and the UK developed a Polaris improved-front-end (IFE) codenamed Chevaline, designed to counter this ABM defence which threatened to completely nullify an independent UK deterrent posture. When Chevaline became public knowledge in 1980, it generated huge controversy as it had been kept secret by the four governments of Wilson, Heath, Wilson (again) and Callaghan, whilst costs rocketed during a period of high inflation, until disclosed by the Thatcher government. By the time it entered service in 1982 it had cost approx £1bn. The final Polaris/Chevaline patrol took place in 1996, two years after the first Trident-carrying submarine sailed on its first patrol.

As well as the establishment at Aldermaston, the UK nuclear weapons programme also has a factory at Burghfield nearby which assembled the weapons and is responsible for their maintenance, and had another in Cardiff which fabricated non-fissile components and a 2000 acre (8 km²) test range at Foulness. Since 1993 the sites have been managed by private consortia. The Foulness and Cardiff facilities closed in October 1996 and February 1997 respectively.

Trident
The UK currently has four Vanguard class submarines based at HMNB Clyde in Scotland, armed with nuclear-tipped Trident missiles. The principle of operation is based on maintaining deterrent effect by always having at least one submarine at sea, and was designed for the Cold War period. One submarine is normally undergoing maintenance and the remaining two in port or on training exercises. It has been suggested that the UK's ballistic missile submarine patrols are coordinated with those of the French.

Each submarine carries 16 Trident II D-5 missiles, which can each carry up to 12 warheads. However, the UK government announced in 1998 that each submarine would carry only 48 warheads, an increase of 50% over the 32 warheads carried by Trident's predecessor, Chevaline, (halving the limit specified by the previous government), which is an average of three per missile. However one or two missiles per submarine are probably armed with fewer warheads for "sub-strategic" use causing others to be armed with more; but this is speculative.

The UK-designed warheads are thought to be selectable between 0.3, 5–10 and 100 kt (1.3, 21–42 and 420 TJ); the yields obtained using either the unboosted primary, the boosted primary, or the entire "physics package"; these yields and similar data are speculative. Although the UK designed, manufactured and owns the warheads, there is evidence that the warhead design is similar to, or even based on, the US W76 warhead fitted in some US Navy Trident missiles, with design data being supplied by the United States through the 1958 US-UK Mutual Defence Agreement. The United Kingdom owns 58 missiles which are shared in a joint pool with the United States government and these are exchanged when requiring maintenance with missiles from the United States Navy's own pool and vice versa.

Replacement for Trident
A decision on the replacement of Trident was made on 4 December 2006. Prime Minister Tony Blair told MPs it would be "unwise and dangerous" for the UK to give up its nuclear weapons. He outlined plans to spend up to £20bn on a new generation of submarines for Trident missiles. He said submarine numbers may be cut from four to three, while the number of nuclear warheads would be cut by 20% to 160. Blair said although the Cold War had ended, the UK needed nuclear weapons, as no-one could be sure another nuclear threat would not emerge in the future.

The new 2010 coalition government agreed "that the renewal of Trident should be scrutinised to ensure value for money. Liberal Democrats will continue to make the case for alternatives." Research and development work continued with an 'Initial Gate' procurement decision, but the 'Main Gate' decision to manufacture a replacement was re-scheduled for 2016, after the next election.

Deployment of US tactical nuclear weapons
Until 1992 UK forces also deployed US tactical nuclear weapons as part of a US-UK dual-key NATO nuclear sharing role. This arrangement commenced in 1958 as Project E to provide nuclear weapons to the RAF prior to a sufficient number of Britain's own nuclear weapons becoming available.

The weapons deployed included nuclear artillery, nuclear demolition mines and warheads for Corporal and Lance missiles in Germany; theatre nuclear weapons on RAF aircraft; Mark 101 nuclear depth bombs on RAF Shackleton maritime patrol aircraft, later replaced by a modern successor, the B-57 deployed on RAF Nimrod aircraft.

The Lance missiles were purchased in 1975, to replace Honest John missiles which had been bought in 1960; and were themselves a replacement for the US Corporal missiles deployed in Germany by the Royal Artillery. Not generally recognised is the fact that the Royal Artillery deployed a numerically greater quantity of US nuclear weapons than the RAF and Royal Navy combined, peaking at 277 in 1976–78; with a further 50 ADMs deployed with another British Army unit, the Royal Engineers, peaking in 1971–81. The dual-key agreement for controlling US tactical nuclear weapons, known as the Heidelberg Agreement, was made on 30 August 1961. The UK sponsored access for the Canadian Army Honest John missile deployments to the US/UK nuclear warhead storage sites.

During the 1980s nuclear armed USAF Ground Launched Cruise Missiles were deployed at RAF Greenham Common and RAF Molesworth. Until about 2006 the US continued to store nuclear weapons in the UK, when approximately 110 tactical B61 nuclear bombs stored at RAF Lakenheath for deployment by USAF F-15E Strike Eagle aircraft were removed.

The UK continues to permit the US to deploy nuclear weapons from its territory, the first having arrived in 1954.

Atomic Weapons Establishment, Aldermaston
The Atomic Weapons Establishment (AWE), Aldermaston (formerly the Atomic Weapons Research Establishment, Aldermaston) is situated just 7 mi north of Basingstoke and approximately 14 mi south-west of Reading, Berkshire, near a village called Aldermaston, bordering with Tadley. It was built in 1949 on the site of a former World War II Royal Air Force base and converted to nuclear weapons research, design and development in the 1950s. Although some early test devices were probably assembled on this site, final assembly of Service-engineered weapons takes place at the nearby site of Burghfield.

Royal Ordnance Factories, Cardiff and Burghfield
Other nuclear weapons sites could be found in Cardiff and Burghfield near Reading, Berkshire. These were the only two Royal Ordnance Factories (ROFs) not privatised in the 1980s.

ROF Cardiff, which closed in 1997, was involved in nuclear weapons programmes since 1961. The site was used for the task of recycling old nuclear weapons and precisely shaping uranium 235 (U235) and metallic beryllium components for the boosted fission devices used as primaries or 'triggers' in modern thermonuclear weapons. ROF Burghfield was a former Filling Factory, opened in 1942, and run as an Agency Factory, by Imperial Tobacco, to fill Oerlikon 20 mm ammunition.

Anti-nuclear movement


The anti-nuclear movement in the United Kingdom consists of groups who oppose nuclear technologies such as nuclear power and nuclear weapons. Many different groups and individuals have been involved in anti-nuclear demonstrations and protests over the years.

One of the most prominent anti-nuclear groups in the UK is the Campaign for Nuclear Disarmament (CND). CND's Aldermaston Marches began in 1958 and continued into the late 1960s when tens of thousands of people took part in the four-day marches. One significant anti-nuclear mobilisation in the 1980s was the Greenham Common Women's Peace Camp. In London, in October 1983, more than 300,000 people assembled in Hyde Park as part of the largest protest against nuclear weapons in British history. In 2005 in Britain, there were many protests about the government's proposal to replace the ageing Trident weapons system with a newer model.

Nuclear posture
UK nuclear posture during the cold war was informed by dependence on the United States. Operational control of the UK Polaris force was assigned to SACLANT, while targeting policy for its missiles was determined, as for the V-bomber force before it, by NATO's SACEUR, while maintaining an independent wholly UK targeting policy for circumstances when a critical national emergency required it to be used alone, without the UK's NATO allies. In these circumstances, the Moscow criterion referred to the ability of the UK to strike back at the highly centralised Soviet decision-making apparatus concentrated in the Moscow area, intended to destroy the ability of the Soviet leadership to remain in control of a Soviet Union otherwise untouched. The early beginnings of studies to increase the likelihood of successful penetration of the Polaris warheads to Moscow can be traced back to 1964, before the Polaris system was deployed, in order to preserve this capability in the face of anti-ballistic missile batteries around Moscow. These studies later materialised as Chevaline.

The UK has relaxed its nuclear posture since the collapse of the Soviet Union. The Labour government's 1998 Strategic Defence Review made reductions from the plans announced by the previous Conservative government:
 * The stockpile of "operationally available warheads" was reduced from 300 to "less than 200"
 * The final batch of missile bodies would not be purchased, limiting the fleet to 58.
 * A submarine's load of warheads were reduced from 96 to 48. This reduced the explosive power of the warheads on a Vanguard class Trident submarine to "one third less than a Polaris submarine armed with Chevaline." However 48 warheads per Trident submarine represents a 50% increase on the 32 warheads per submarine of Chevaline. Total explosive power has been in decline for decades as the accuracy of missiles has improved, therefore requiring less power to destroy each target. Trident can destroy 48 targets per submarine, as opposed to 32 targets that could be destroyed by Chevaline.
 * Submarines missiles would not be targeted, but rather at several days "notice to fire".
 * Although one submarine would always be on patrol it will operate on a "reduced day-to-day alert state". A major factor in maintaining a constant patrol is to avoid "misunderstanding or escalation if a Trident submarine were to sail during a period of crisis."

Current UK posture as outlined in the Strategic Defence Review of 1998 is as it has been for many years. Only the delivery methods have changed. Trident SLBMs still provide the long-range strategic element as they have done for some years. Until 1998 the free-fall WE.177A, WE.177B and WE.177C bombs provided an aircraft-delivered sub-strategic option in addition to their designed function of tactical battlefield weapons. With the retirement of WE.177, a sub-strategic warhead is stated by Ministers to be incorporated into some (but not all) Trident missiles deployed. The exact mix of weapons on each submarine is unknown as is the numbers and warhead yield.

Nuclear weapons control
The precise details of how a British Prime Minister would authorise a nuclear strike remain secret, although the principles of the Trident control system is believed to be based on the plan set up for Polaris in 1968, which has now been declassified. A closed-circuit television system was set up between 10 Downing Street and the Polaris Control Officer at the Northwood Headquarters of the Royal Navy. Both the Prime Minister and the Polaris Control Officer would be able to see each other on their monitors when the command was given. If the link failed – for instance during a nuclear attack or when the PM was away from Downing Street – the Prime Minister would send an authentication code which could be verified at Northwood. The Commander in Chief would then broadcast a firing order to the Polaris submarines via the Very Low Frequency radio station at Rugby. The UK has not deployed control equipment requiring codes to be sent before weapons can be used, such as the U.S. Permissive Action Link, which if installed would preclude the possibility that military officers could launch British nuclear weapons without authorisation.

Until 1998, when it was withdrawn from service, the WE.177 bomb was armed with a standard tubular pin tumbler lock (as used on bicycle locks) and a standard allen key was used to set yield and burst height. Currently, British Trident commanders are able to launch their missiles without authorisation, whereas their American colleagues cannot. At the end of the Cold War the U.S. Fail Safe Commission recommended installing devices to prevent rogue commanders persuading their crews to launch unauthorised nuclear attacks. This was endorsed by the Nuclear Posture Review and Trident Coded Control Devices were fitted to all U.S. SSBNs by 1997. These devices prevented an attack until a launch code had been sent by the Chiefs of Staff on behalf of the President. The UK took a decision not to install Trident CCDs or their equivalent on the grounds that an aggressor might be able to wipe out the British chain of command before a launch order had been sent.

In December 2008 BBC Radio 4 made a programme titled The Human Button, providing new information on the manner in which the United Kingdom could launch its nuclear weapons, particularly relating to safeguards against a rogue launch. Former Chief of the Defence Staff (most senior officer of all British armed forces) and Chief of the General Staff (most senior officer in the British Army), General Lord Guthrie of Craigiebank, explained that the highest level of safeguard was against a prime minister ordering a launch without due cause: Lord Guthrie stated that the constitutional structure of the United Kingdom provided some protection against such an occurrence, as while the Prime Minister is the chief executive and so practically commands the armed services, the ultimate commander-in-chief is the Monarch, to whom the chief of the defence staff could appeal: ''"the chief of the defence staff, if he really did think the prime minister had gone mad, would make quite sure that that order was not obeyed... You have to remember that actually prime ministers give direction, they tell the chief of the defence staff what they want, but it's not prime ministers who actually tell a sailor to press a button in the middle of the Atlantic. The armed forces are loyal, and we live in a democracy, but actually their ultimate authority is the Queen."''

The same interview pointed out that while the Prime Minister would have the constitutional authority to fire the Chief of the Defence Staff, he could not appoint a replacement as the position is appointed by the monarch. During the Cold War the Prime Minister was also required to name a senior member of the cabinet as his/her designated-survivor, who would have the authority to order a nuclear response in the event of an attack incapacitating the Prime Minister, and this system was re-adopted after the September 11 attacks.

The programme also addressed the workings of the system; detailing that two persons are required to authenticate each stage of the process before launching, with the submarine captain only able to access the firing trigger after two safes have been opened with keys held by the ship's executive and weapons engineering officers. It was explained that all Prime Ministers issue hand-written orders, termed the letters of last resort, seen by their eyes only, sealed and stored within the safes of each of the four Royal Navy Vanguard class submarines. These notes instruct the submarine commander of what action to take in the event of the United Kingdom being attacked with nuclear weapons that destroy Her Majesty's Government in the United Kingdom and/or the chain of command.

Although the final orders of the Prime Minister are at his or her discretion, and no fixed options exist, according to the December 2008 BBC Radio 4 documentary The Human Button there were four known options: retaliating with nuclear weapons, not retaliating with nuclear weapons, the submarine commander uses his own judgement, or the submarine commander places himself under United States or Australian command if possible. This system of issuing notes containing orders in the event of the head of government's death is said to be unique to the United Kingdom (although the concept of written last orders, particularly of a ship's captain, is a naval tradition), with other nuclear powers using different procedures. The letters are destroyed unopened whenever a Prime Minister leaves office.

All relevant former prime ministers have supported an "independent nuclear deterrent", as does incumbent David Cameron. Only one former Prime Minister, Lord Callaghan, has given any insight on his orders: Callaghan stated that, although in a situation where nuclear weapon use was required – and thus the whole purpose and value of the weapon as a deterrent had failed – he would have ordered use of nuclear weapons, if needed: ...if we had got to that point, where it was, I felt it was necessary to do it, then I would have done it (used the weapon)...but if I had lived after pressing that button, I could have never forgiven myself. Lord Healey, Secretary of State for Defence and "alternate decision-taker" under Prime Minister Harold Wilson, said that in the event of Soviet nuclear weapons attacking the United Kingdom and the Prime Minister had been killed or incapacitated, he would not have ordered a retaliation.

The process by which a Trident submarine would determine if the British government continues to function includes, amongst other checks, establishing whether BBC Radio 4 continues broadcasting.

The special relationship
The 1958 'Agreement For Cooperation on the Uses of Atomic Energy for Mutual Defence Purposes' also known as the 'Mutual Defence Agreement' was renewed in 1994 and again in 2005.

Cost
The current Trident system cost £12.6bn (at 1996 prices) and costs £280m a year to maintain. Options for replacing Trident range from £5bn for the missiles alone to £20-30bn for missiles, submarines and research facilities. At minimum, for the system to continue after around 2020, the missiles will need to be replaced.

Legality

 * See also International Court of Justice advisory opinion on the Legality of the Threat or Use of Nuclear Weapons
 * See also Nuclear Non-Proliferation Treaty

After the British government announced its plans to refurbish its Trident SLBM missiles and build new submarines to carry them, it published a white paper The Future of the United Kingdom’s Nuclear Deterrent in which it stated that the renewal is fully compatible with the United Kingdom's treaty commitments and international law. These arguments are summarised in a question and answer briefing published by UK Permanent Representative to the Conference on Disarmament

At the start of the House of Commons debate to authorise the replacement of Trident, Margaret Beckett stated:

The subsequent vote was won overwhelmingly, including unanimous support from the opposition Conservative Party.

The Government position remains that it is abiding by the NPT legally in renewing Trident and Britain has the right to possess nuclear weapons, a position reiterated by Tony Blair in PMQs on 21 February 2007.

In contrast, reports by Philippe Sands QC, and by Rabinder Singh QC and Professor Christine Chinkin, used in the case against, were commissioned by the activist groups Greenpeace and Peace Rights respectively. Both groups are opposed to the renewal, use, or proliferation of nuclear weapons.

Furthermore, the British Government and NATO do not recognise advisory opinion of the ICJ, as interpreter of IHL and referred to by Sands et al., (see Advisory Opinion) with regard to use of nuclear weaponry as legally binding.

This position is held in common with all five nuclear states as defined in the NPT. However, only the United Kingdom has expressed its opposition to the establishment of a new legally binding treaty to prevent the threat or use of nuclear weapons against non-nuclear states by its vote in the United Nations General Assembly in 1998.

One view is that the white paper The Future of the United Kingdom’s Nuclear Deterrent stands in contrast to two counsel's opinions. The first, commissioned by Peacerights, was given on 19 December 2005 by Rabinder Singh QC and Professor Christine Chinkin of Matrix Chambers. It addressed '...whether Trident or a likely replacement to Trident breaches customary international law'

Drawing on the International Court of Justice (ICJ) opinion, Singh and Chinkin advised that:

The second opinion was commissioned by Greenpeace and given by Philippe Sands QC and Helen Law, also of Matrix Chambers, on 13 November 2006. The opinion addressed

With regards to the jus ad bellum, Sands and Law advised that

The phrase "very survival of the state" is a direct quote from paragraph 97 of the ICJ ruling. With regards to international humanitarian law, they advised that

Finally, with reference to the NPT, Sands and Law advised that