Dido-class cruiser

The Dido class was a class of sixteen (including the Bellona sub-class) light cruisers built for the Royal Navy. The design was influenced by the Arethusa-class light cruisers. The first group of three ships was commissioned in 1940, the second group (six ships) and third group (two ships) were commissioned in 1941–1942. The Bellona-class ships commissioned between 1943 to 1944. Most members of the class were named after figures of Greek mythology.

They were designed as fleet escorts to protect heavier units from both light surface forces and aircraft.The selection of the 5.25 turret as the main armament with 80 lb shells the heaviest liftable by man, was to maximise surface action power while providing some anti air capability in the confined Mediterranean. This remains questionable. The Dido and Improved Didos were flawed because the 5.25 shells weight meant fire rates of only 7.5rpm were sustainable with short bursts of 10rpm in the first 2 minutes. RN 4.5 mounts were more successful when applied in the DP role in these ships. Small 6 inch gunned cruisers like the Arethusa were arguably better in the Mediterranean while the Improved Dido's main role as a picket ship in the Pacific in late WW2 and postwar with the RNZN was hindred by short range and general overloading of the class. The (1933) 6 inch Leanders might have more useful as pickets with long range and long life. The Board of Admiralty and many of the RN's leading ship designers strongly favoured the 5.25 ships. Many thought all new cruisers should have had no more powerful armament from 1942 because the 5.25 turret, weighing 78-96 tons, was so much more compact above and below decks compared with 6 inch Mk 23 turret and Mk 24,25 and Mk 26 semi and fully auto turrets being developed at the time. The latter weighed 175-205 tons and the 5.25 appeared to have plenty of potential for automation and better shells. The 5.25 merits had been borne out by good results in actions against Italian cruisers and in convoy defence in the Mediterranean in 1941-3. The only real problem with the type was the early war shortage of gun-mountings and a need to stiffen them forward to take the weight of the forward turrets.

Armament
The class were intended to be armed with ten 5.25 inch (133 mm) guns in five twin turrets, which were of the same circular design as the secondary armament in the King George V-class battleships. A shortage of the guns, due to difficulties in manufacturing them, led to the first group being armed with only eight 5.25 inch guns in four twin turrets. The fifth twin turret was added later to Dido only. The first group was also armed with a 4 inch (102 mm) gun and two quadruple QF 2 pounder (40 mm) "pom-poms".

The second group had the five twin 5.25 inch guns but did not have the 4 in (102 mm) gun. The third group's armament was changed due to the shortage of 5.25 in guns, being armed with eight 4.5 inch (113 mm) guns in four twin turrets instead. The 4.5 inch gun was better suited to the primary anti-aircraft role of the Dido class. The 4.0 inch (102 mm) gun was also fitted and its 2 pounder armament was increased from eight to ten.

The Bellona subclass differed in appearance somewhat from their predecessors. They had eight 5.25 inch (133 mm) RP10MkII guns in four twin turrets and had vastly improved anti-aircraft armament, with twelve 2 pounder guns and twelve Oerlikon 20 mm cannons. The bridge of the Bellona class was lowered by one deck compared to the previous three groups, which allowed full radar control to be fitted to the 5.25 inch (133 mm) turrets and 2 pounders, due to the decreased topweight. These ships used the HACS high angle fire control system. The two funnels were more upright than the raked ones of the original Dido class.

Service
In World War II, the Dido class saw much action, including the battle of Cape Matapan, the Second Battle of Sirte, Operation Torch, Operation Overlord and the battle of Okinawa, as well as many other duties in the Mediterranean and Pacific. The class lost five ships during the war (Bonaventure, Charybdis, Hermione, Naiad, and Spartan); in addition the Scylla was badly damaged by a mine and declared a Constructive Total Loss. The post-war survivors continued in service; all were decommissioned by the 1960s. Bellona, Black Prince and Royalist were lent to the Royal New Zealand Navy post-World War II. In 1956, Diadem was sold to Pakistan and renamed Babur.

Didos
Bonaventure completed with only four twin 5.25 in turrets because of shortages and received a 4 inch starshell gun in X position. She had received a radar set before October 1940 but was otherwise unaltered.

Naiad completed with five turrets. She received five single 20 mm in September 1941 and had radar Type 279 by this time.

HMS Phoebe (43) completed with four turrets and was fitted with a 4 inch in Q position forward of the bridge. The latter was landed during her refit between November 1941 and April 1942 at New York, along with the .5 inch machine guns and Type 279 radar, while a quadruple 2 pdr supplanted the 4 inch and eleven single 20 mm guns were fitted. Radars were now Type 281, 284 and 285. The A turret was temporarily removed at the end of 1942 after torpedo damage. During repairs in the first six months of 1943, all three quadruple 2 pdr were landed, as were seven single 20 mm, to be replaced by three quadruple 40 mm Bofors guns and six twin 20 mm. Radar Type 272 was also fitted. A turret was replaced in July 1943. Her light anti-aircraft weaponry in April 1944 was twelve 40 mm (3 × 4) and sixteen 20 mm (6 × 2, 4 xl).

Dido had four turrets and a 4 inch similar to Phoebe. The 4 in and the machine guns were removed in the latter half of 1941 at Brooklyn Navy Yard, when Q 5.25 in turret was shipped and five single 20 mm were fitted. In the early summer of 1943 three single 20 mm were exchanged for four twin 20 mm and the radar outfit was altered by the addition of Types 272, 282, 284 and 285. April 1944 lists show only eight 20 mm. Euryalus completed with her designed armament. In September 1941 the .5 in MGs were landed and five single 20 mm fitted. Two more were added by September 1942. By mid-1943 two single 20mm had been removed and four twin 20 mm shipped. The type 279 radar was replaced by types 272, 281, 282 and 285. In a long refit from October 1943 to July 1944, Q turret was replaced by a quadruple 2 pdr and two twin 20 mm were fitted. Radar 271 and 272 were removed and types 279b, 277 and 293 fitted.

Hermione also completed as a five-turret ship. She had the .5 in MGs removed in October/November 1941 and received five single 20 mm.

Sirius completed with five turrets and five 20 mm. She had received two more 20 mm by mid-1943. One of these was landed at Massawa at the end of 1943 and two 40 mm Bofors Mk III were fitted. She is listed as having only seven 20 mm as light AA in April 1944. By April 1945 she had two Mk III 40 mm fitted and had landed two single 20 mm.

Cleopatra was completed with two 2 pdr in 1942 in lieu of the .5 in MGs but these were removed in the middle of the year and replaced by five 20 mm. A sixth 20 mm was added in mid-1943. During repairs between November 1943 and November 1944, Q turret was removed, as were two quadruple 2 pdr and five 20 mm. Three quadruple 40 mm Bofors and six twin 20 mm were fitted and the singles numbered four.

Argonaut completed with four single 20 mm in lieu of the .5 in MGs. She had Q turret removed during repairs in 1943/44, and lost the four single 20 mm. She received a quadruple 2 pdr in lieu of the 5.25 in, and had five twin 20 mm fitted. By April 1944 her light AA comprised three quadruple 2 pdr, six twin power-operated 20 mm and five single. By the end of the war with Japan she had received five 40 mm Bofors and three single 40 mm Bofors Mk III.

Scylla completed with four twin 4.5 in Mk III in UD MK III mountings because of a shortage of 5.25 in mountings. The forward superstructure was considerably modified to accommodate these and also to increase crew spaces. Her light AA on completion was eight single 20 mm. Six twin power-operated 20 mm were added at the end of 1943.

Charybdis also completed with four twin 4.5 inch, and had in addition a single 4 in Mk V for-ward of X mounting. Her light AA at completion was four single 20 mm and two single 2 pdr. The 4 inch starshell gun and two single 2 pdr were removed and replaced by two twin and two single 20 mm, probably in 1943.

Bellonas
Spartan received no alterations as far as is known.

Royalist was converted to an Escort Carrier Squadron flagship immediately on completion, when an extra two twin 20 mm were fitted as well as four single 20 mm. She was the only ship to receive an extensive postwar modernisation ordered for the RN but was later sold to New Zealand. Plans were drawn up to fully modernise the 4 improved Didos with either four twin 3 inch L70s or Mk 6 4.5s. However, that would have required new broad beamed Didos to be built as was seriously considered in 1950-54 because the Royalist magazines could only have had space for 3min 20 sec, firing of the 3 inch guns.The Refit of the Royalist was shortened and that of Diadem abandoned because new steam turbines were regarded as necessary and unafforabable. The Royalist's reconstruction however, like that of the earlier job on Newfoundland, incorporates much of the RNs late 1940s and early 1950s view of a desirable cruiser. The Royalist's 5.25 armament was given some of the improvements of the final 5.25 mounts built for Vanguard but not the extra space or power ramming. Also added was a secondary armament or STAAG auto twin 40mm and new 293, 260 and 275M radar and lattice mast. (Loaned to RNZN in 1956, in exchange for Bellona).

Bellona had four single 20 mm added by April 1944, and received an extra eight single 20 mm by April 1945. (Loaned to the RNZN after the war and operational 1946-52).

Black Prince and Diadem also received eight single 20 mm, and had a further two twin 20 mm by early 1945. (Black Prince was loaned to the RNZN after the war and was operational briefly in 1947 before part of its crew mutinied and were discharged. Between 1952 and 1955, which included a visit to the 1953 Fleet Review at Spithead; Diadem was sold to Pakistan in 1956 after a modest refit with 293 and 281 radar and standardised 40mm twin and single light a/a. Its 5.25s fired in Pakistans brief war with India in 1961. It became a cadet training ship in 1962 when Pakistan renamed it Babur).

In popular culture

 * HMS Ulysses (1955 novel by Alistair Maclean)Based on the role of the Royalist in protecting late war, Arctic convoys to Murmansk, MacLean puts emphasis on the high quality radar fit and the ships primary AD role from the start. Also noted is the ships exceptional trial speed of supposedly near 39 knots (myth ?); the exceptional difficulty of the crew sleeping in these small cruisers, which was a characteristic of every Royalist crew from 1943 to 1965 and its supplementary a/s capability.
 * In the 1953 film of C.S.Forester's Brown on Resolution, (called Sailor of the King in Britain, and Single-handed in the USA), the Dido-class HMS Cleopatra (33) plays both the fictional Royal Navy ships "HMS Amesbury" and "HMS Stratford". As Amesbury she is heroically sunk by the more powerful German raider Essen, (portrayed by HMS Manxman (M70) with large mock-up gun turrets), and as Stratford she triumphs at the end of the story.  The two battle sequences depict this open-bridge light-cruiser firing her guns and torpedoes in some detail.