Town - class cruiser ( 1936 ) The Town class was a 10 - ship class of light cruiser s of the Royal Navy . The Towns were designed to the constraints imposed by the London Naval Treaty of 1930 . The ships were built in three distinct sub - classes , the " Southampton " , " Gloucester " and " Edinburgh " classes respectively , each sub - class adding on further weaponry . Armament . Like their US and Japanese counterparts of that era , the Town - class cruisers were " light cruisers " in the strict terms of the Treaty . The London Treaty defined a " light cruiser " as one having a main armament no greater than 6 . 1 in ( 155 mm ) calibre , all three major naval powers sought to circumvent the limitations on heavy cruiser numbers by building " light cruisers " that were equal in size and effective power to heavy cruiser s . These ships made up for their smaller calibre guns by carrying larger numbers of them . All of these ships carried BL 6 - inch Mk XXIII guns in triple turrets , with the centre gun mounted behind the two outer guns to prevent interference between the shells in flight and to give the gunners more room to work in . The turret roofs had cutouts at the front to allow extreme elevation , originally intended to give the guns an anti - aircraft capability , although the guns could not be trained or manually loaded quickly enough in practice for continuous anti - aircraft fire so the Royal Navy designed the ABU , which allowed the guns to be preloaded with time fuzed shells , and then fired when the target aircraft reached the preset range . These ships were equipped with the HACS AA fire control system for the secondary armament and the Admiralty Fire Control Table for surface fire control of the main armament . " Southampton " class . The " Southampton " class was the first and the subsequent two sub - classes were also known as modified or improved " Southampton " s . They had originally been built in response to the US " Brooklyn " - class and Japanese " Mogami " - class light - cruisers . " Gloucester " class . The subsequent " Gloucester " s had a redesigned deck and received thicker armour on the gun turrets . " Edinburgh " class . The " Edinburgh " class were longer at compared to , initially to allow an increase in the main armament from twelve 6 in ( 152 mm ) guns in four triple turrets as in the two previous sub - classes , to sixteen 6 in guns in four quadruple turrets . The idea was soon shelved however , due to the difficulties in actually manufacturing an effective quadruple 6 in turret , and so the class reverted to the original main armament design , although improved through a " long trunk " Mk XXIII turret design , which reduced the crew requirements and increased the speed of the ammunition hoists . Four extra 4 in ( 102 mm ) " High Angle Low Angle " guns and eight extra 2 - pounder ( 40 mm ) gun s and further armour protection were added instead . Later improvements . All were heavily modified during the Second World War and after the Korean War ; , and had one aft turret replaced by two quad 40 mm Bofors guns during the Second World War , since there was insufficient space to fit the needed extra anti - aircraft guns and retain the turret . This was not a problem in the " Edinburgh " s , because they were longer and had more room . They still had substantial modifications to their weaponry , including addition of 40 mm Bofors guns . The addition of radar equipment during the Second World War , aided the ships ' combat effectiveness . Service . The first Town - class ship was launched in 1936 and commissioned in 1937 , just two years before the outbreak of war . The Town class saw much service during the Second World War and took in many famous actions , such as the sinking of the German battleship . Four were sunk during the war , , , , and . Many of the surviving ships saw successful service during the Korean War and continued in active service to the end of the 1950s . The last Town - class ship to be scrapped was " Sheffield " in 1967 . One Town - class warship — — remains , moored on the River Thames in London as a museum - ship of the Imperial War Museum , a role she has performed since 1971 .