William Penney, Baron Penney

William George Penney, Baron Penney OM, KBE PhD, DSc,, FRS, FRSE, FIC, Hon FCGI (24 June 1909 – 3 March 1991), was an English mathematician and professor of mathematical physics at the Imperial College London and later the rector of Imperial College. He is acknowledged as having a leading and integral role in the development of Britain's nuclear programme, a clandestine programme started in 1942 during World War II which produced the first British atomic bomb in 1952.

As the head of the British delegation working in the Manhattan Project, Penney initially carried out calculations to predict the damage effects generated by the blast wave of an atomic bomb. Upon returning home, Penney directed Britain's own nuclear weapons directorate, codename Tube Alloys, and directed scientific research at the Atomic Energy Research Establishment which resulted in the first detonation of a British nuclear bomb, (see codename Operation Hurricane) in 1952. After the test, Penney became chief adviser to the newly created British government's United Kingdom Atomic Energy Authority (UKAEA). He was later chairman of the authority, which he used in international negotiations to control nuclear testing with the Partial Nuclear Test Ban Treaty.

Penney's notable scientific contributions included the mathematics for complex wave dynamics, both in shock and gravitational waves, proposing optimization problems and solutions regarding the hydrodynamics wave which played a major role in the applications materials and the metallurgy. During his later years, Penney lectured in mathematics and physics, and was tenured as the Rector of the Imperial College London until his death.

Early life and education
William George "Bill" Penney was born in Gibraltar, British Overseas Territory, on 24 June 1909. His father was a sergeant-major in the British Army's Ordnance Corps who was then serving overseas. Penney was raised in Sheerness, Kent, and attended the local technical school in Colchester where he completed his technical studies. From 1924 to 1926, he was educated at Sheerness Technical High School for Boys where he displayed a talent for science.

In 1927, his passion for science landed him in a local science laboratory where he worked there as an assistant which helped him to gain a scholarship to study science at the world's prestigious college, the Imperial College of Science. He applied and was admitted to the Imperial College Faculty of Natural Sciences where he began taking courses on mathematics, particularly courses on Linear Algebra, Calculus, Partial differential equations and differential geometry. His talent was recognised by the Governor's Prize for Mathematics from the faculty of science. In 1929 Penney graduated, obtaining the B.Sc. in Mathematics with First Class Honours at age 20. Penney was admitted to the post-graduate department that year, and earned his M.Sc. in mathematics in 1931. Then he was offered a research position at the London University, where he studied for a doctorate. In 1932, Penney was awarded the Ph.D. in Mathematics after submitting his doctoral thesis containing work on optimization and cross section of the physical properties of sold-state crystals.

Penney accepted a Commonwealth Fund Fellowship and first traveled to United States where he became foreign research associate at the University of Wisconsin–Madison, returning to England soon after. In England, Penney was granted the 1851 Exhibition Scholarship to attend the Trinity College at Cambridge University. He changed his mathematical career to physics, and conducted a thorough research and theoretical investigation into the structure of metals and the magnetic properties of crystals.

In 1935, Penney submitted his final thesis and obtained a D.Sc. in Mathematical Physics from the University of Cambridge; his thesis contained the fundamental work in the applications of quantum mechanics to the physics of crystals. In 1936, he was elected to the Stokes studentship at Pembroke College, Cambridge, but in the same year he returned to London and was appointed Reader in Mathematics at Imperial College London, a post he held from 1936 to 1945. As a recognized prodigy at Imperial College he was set for a distinguished academic career until World War II intervened.

World War II
At the start of World War II, Penney's leading-edge research into the applications of physics was noticed, and he was offered a research position with the Royal Navy. He had made significant contributions made to the application of collisions, explosion events that created  shock waves, and applications involving military use of hydrodynamics and gravitational waves. The Admiralty and Home Office asked Penney to investigate problems connected with the properties of under-water blast waves from high explosives, a subject of great importance in designing ships and torpedoes. With Royal Navy engineer officers he designed and supervised development of the Mulberry harbours to be placed off the Normandy beaches during the D-Day invasion. These mobile breakwaters would protect the landing craft and troops from the Atlantic rollers. In 1943, he was released from his Royal Navy work, and went to the physics faculty of the Imperial College London, his alma mater.

Then he joined Tube Alloys the secret nuclear weapon directorate, and shortly before D-Day in 1944, Penney was made head of the British delegation to the Manhattan Project, when a large team of British scientists joined the American atomic bomb project. Penney and others went to the Los Alamos Laboratory.

The Manhattan Project
At Los Alamos Penney worked on the use of the atomic bomb, particularly the height at which it should be detonated. He quickly gained recognition for his scientific talents, and also for his leadership qualities and ability to work in harmony with others. Within a few weeks of his arrival he was added to the core group of scientists making key decisions in the direction of the program. Other members of that team included J. Robert Oppenheimer, John von Neumann, Norman F. Ramsey and Captain William Parsons of the United States Navy (USN).

One of Penney's assignments at Los Alamos was to predict the damage effects from the blast wave of an atomic bomb. On 16 July 1945, Penney was an observer at the Trinity test detonation. He was there to observe the effect of radiant heating in igniting structural materials, and had also designed apparatus to monitor the blast effect of the explosions. The Americans considered him to be among the five most distinguished British contributors to the work. General Leslie Groves, overall director of the Manhattan Project, later wrote: "vital decisions were reached only after the most careful consideration and discussion with the men I thought were able to offer the soundest advice. Generally, for this operation, they were Oppenheimer, Von Neumann, Penney, Parsons and Ramsey."

Penney went to Washington for a top secret committee target selection meeting. He recommended Hiroshima and Nagasaki because of the hills surrounding the target which he said would create maximum devastation. He gave valuable advice to the height of the bomb detonation so that the fireball would not touch the earth and also to avoid permanent radiation contamination on the ground. The U.S. nuclear team repeatedly attempted to recruit Penney as a permanent member, without success.

Along with RAF Group Captain Leonard Cheshire, he accompanied the American Team to Tinian Island from which the Hiroshima and Nagasaki missions were flown. On 9 August 1945 he witnessed the bombing of Nagasaki. The US authorities had controversially stopped them seeing the Hiroshima detonation, but at the last minute Penney and Cheshire were granted permission to fly in the B-29 Big Stink, one of the observation planes that accompanied the Nagasaki mission bomber Bockscar. Due to the belated permission, Big Stink missed its rendezvous with the bomber at Nagasaki. They saw the Nagasaki detonation from the air at a distance. As the leading expert on the effects of nuclear weapons, Penney was a member of the team of scientists and military analysts who entered Hiroshima and Nagasaki following the Japanese surrender on 15 August 1945 to assess the effects of nuclear weapons.

Post war
At the end of the war the British government, now under Labour Prime Minister Clement Attlee, believed that America would share the technology that British leaders saw as a joint discovery under the terms of the 1943 Quebec Agreement. In December 1945 PM Attlee ordered the construction of an atomic pile to produce plutonium and requested a report to detail requirements for Britain's atomic bombs. Penney returned to England and intended to resume his academic career, but was approached by C. P. Snow and asked to take up post as Chief Superintendent Armament Research (CSAR, called "Caesar") at Fort Halstead in Kent, as he suspected Britain was going to have to build an atomic bomb of its own and the government wanted Penney in this job. As CSAR he was responsible for all types of armaments research.

In 1946, at the request of General Leslie Groves and the US Navy, Penney returned to the United States where he was put in charge of the blast effects studies for Operation Crossroads. In July, he was present at Bikini Atoll in the Marshall Islands and wrote the after action reports on the effects of the two nuclear detonations. His reputation was further enhanced when, after the sophisticated test gauges failed, he was able to determine the blast power using observations from simple devices (empty oil drums).

The British Nuclear Weapons Programme
However the passing of the McMahon Act (Atomic Energy Act) by the Truman administration in August 1946 made it clear that Britain would be no longer be allowed access to US atomic research. Penney left the United States and returned to England where he initiated his plans for an Atomics Weapons Section, submitting them to the Lord Portal (Marshal of the Royal Air Force) in November 1946. During the winter of 1946-1947, Penney returned to the United States, where he served as a scientific adviser to the British representative at the American Atomic Energy Commission. With almost all other aspects of atomic co-operation between the countries at an end, Penney's personal role was seen as keeping the contact alive between the parties.

Attlee's government decided that Britain required the atomic bomb to maintain its position in world politics. In the words of Foreign Secretary Ernest Bevin - "We've got to have it and it's got to have a bloody Union Jack on it." Officially, the decision to proceed with the British atomic bomb project was made in January 1947 - however arrangements were already under way. The necessary plutonium was on order from Harwell and in the Armaments Research Department of the Ministry of Supply, an Atomic Weapons Section was being organised. The project was based at the Royal Arsenal, Woolwich and was code-named High Explosive Research (or HER).

In May 1947, Penney was officially named to head the HER project. The following month Penney began assembling teams of scientists and engineers to work on the new technologies that had to be developed. In June 1947, Penney gathered his fledgling team in the library at the Royal Arsenal and gave a two-hour talk on the principles of the atomic bomb. Centred at Fort Halstead, the work proceeded on schedule. In 1950, the first bomb was expected to ready within two years, and would require a test.

AWRE
The research was spread across several test facilities in the UK, with confusing lines of authority and responsibility. The bomb design was also complex and innovative; although it started off with the Nagasaki bomb design, completely new methods of arming and of electrical detonation were used. It was realized that a single site was required, and in April 1950 an abandoned World War II airfield, RAF Aldermaston in Berkshire was selected as the permanent home for the British nuclear weapons programme. In 1951 the first scientific staff arrived at Aldermaston, and soon after the HER project vacated the Royal Arsenal. On 3 October 1952, under the code-name "Operation Hurricane", the first British nuclear device was successfully detonated off the west coast of Australia in the Monte Bello Islands.

Penney was also aware of the public relations issues associated with the tests, and made clear-speaking presentations to the Australian press. Before one series of tests the Australian High Commissioner described his press presence: "Sir William Penney has established in Australia a reputation which is quite unique: his appearance, his obvious sincerity and honesty, and the general impression he gives that he would rather be digging his garden – and would be, but for the essential nature of his work – have made him a public figure of some magnitude in Australian eyes".

UKAEA
In 1954, nuclear development was transferred from the Ministry of Supply (MoS) to the newly formed United Kingdom Atomic Energy Authority (UKAEA). From 1954 to 1967, Sir William served on the UKAEA Board, becoming Chairman in 1962. Under his leadership the first British hydrogen bomb was developed and tested in May 1957.

Imperial College
The Rt Hon Lord Penney was Rector of Imperial College London from 1967-1973. The college built and named the William Penney Laboratory in his honour in 1987

Legacy and honours
In later years he admitted to qualms about his work but felt it was necessary. When aggressively questioned by the McClelland Royal Commission investigating the test programmes at Monte Bello and Maralinga in 1985, he acknowledged that at least one of the 12 tests probably had unsafe levels of fallout. However, he maintained that due care was taken and that the tests conformed to the internationally accepted safety standards of the time, a position which was confirmed from official records by Lorna Arnold. McClelland broadly accepted Penney's view but anecdotal evidence to the contrary received wide coverage in the press. By promoting a more Australian nationalist view, then current in the government of Bob Hawke, McClelland had also identified "villains" in the previous Australian and British administrations. As a senior witness Penney bore the brunt of the allegations, and his health was badly affected by the experience. He died a few years later at his home in the village of East Hendred, aged 81.

In his obituary in the New York Times he was credited as the father of the British atomic bomb. The Guardian described him as its "guiding light", and his scientific and administrative leadership was said to be crucial in its successful and timely creation. His leadership of the team that exploded the first British hydrogen bomb at Christmas Island was instrumental in restoring the exchange of nuclear technology between Britain and the USA in 1958, and he was credited as playing a leading part in the negotiations which led to the treaty forbidding atmospheric nuclear tests in 1963.

His Kronig-Penney model for the behaviour of an electron in a periodic potential is still taught and used today in solid-state physics, and is used to explain the origin of band gaps.

Honours
During his lifetime William Penney was made a Commonwealth Fund Fellow at University of Wisconsin–Madison (1932); Fellow of the Royal Society (1946); Fellow of the Royal Society of Edinburgh (1970). Among the honours he received was the Rumford Medal by the Royal Society (1966). He was awarded an Honorary Degree (Doctor of Science) by the University of Bath in 1966. For services to the United States, he was one of the first recipients of the United States Medal of Freedom (with Silver Palm), awarded by President Harry S. Truman. For his services to Britain he was appointed an Officer of the Order of the British Empire (OBE; 1946); raised to Knight Commander of the order (KBE; 1952); made a life peer, taking the title Baron Penney, of East Hendred in the Royal County of Berkshire (1967); awarded the Order of Merit (1969). He served on the board of the United Kingdom Atomic Energy Authority (from 1954–1967) and became its Chairman (1962–1967).