Dido - class cruiser The " Dido " class was a class of sixteen ( including the " Bellona " sub - class ) light cruiser s 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 battleship s . 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 ) gun s 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 cannon s . 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 " . Ship modifications . " Dido " s . " 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 . " 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 . " Bellona " s . " 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 " ) .