File:HMS Scylla (98) Model.jpg

English: A model of the Dido Class Light Cruiser HMS Scylla at the Glasgow Transport Museum, 2 March 2007.

Eleven Dido Class cruisers were launched in 1939-41 and completed in 1940-42 and five Modified Dido (or Bellona) Class vessels were launched in 1942 and completed in 1943-44. Although often described as AA cruisers, in fact they were conceived as trade protection cruisers to complement the larger 12x6” gunned 8,500 ton Crown Colony Class of fleet cruisers then being built at the same time. They were based on the 6x6” gunned 5,250 ton Arethusa Class of 1935-37 which had been regarded as too small to be regarded as effective fleet cruisers (although in fact they turned out to be very effective); instead of 6” guns, it was planned that the Didos would be armed with a new design of 5.25” guns and turret which, though optimised for surface use, could be used as an AA weapon and were therefore a dual purpose weapon. 5.25” was considered the largest practicable AA gun, although in service the turret’s training and elevating speed proved somewhat slow in tracking fast moving aircraft. On the other hand, their air-burst was considered devastating.

The Didos emerged as a very innovative design with an unprecedented five twin turrets for its main armament with three stacked in the fore positions of A, B and C (and two in X & Y). Although this potentially raised the centre of gravity of the ship, this was counterbalanced by the first use of aluminium in considerable parts of the forward superstructure and bridge. The Didos measured 512 ft x 50.6 ft x 16.6 ft, with a displacement of 5,600 tons and a designed armament of 10x5.25”DP guns, 8x2 pdr AA pom poms guns (2x4), 8x0.5” mg AA and 8x18” TT (2x4). Their 62,000 shp turbines and 4 screws gave them a speed of 32 kts (although there is a claim that one ship reached 39 kts on trial!).

The outbreak of WWII led to a shortage of bauxite imports whilst what aluminium was produced was prioritised to aircraft production. This resulted to some ships having an all steel superstructure. This, together with delays building the complex 5.25” gun turrets, led to three ships being completed with only four 5.25” turrets and a 4” gun, although the fifth turret was later added on some ships. However, subsequently several ships had a 5.25” turret removed and replaced by various combinations of 1-3 twin/quadruple 40mm and/or 1-3 quadruple pom poms AA guns plus single/twin 20mm AA guns. Moreover, two ships –HMS Scylla and HMS Charybdis - were completed with a completely different armament of 8x4.5” DP (4x2) guns (which, if less hard-hitting in the surface role, was a more effective AA weapon that the 5.25” guns), 1x4” gun, 24x2 pdr AA pom poms (3x4), 8x0.5” mg AA (2x4), 6x21” TT (2x3). By the end of the war Scylla’s armament was 8x4.5” DP (4x2), 8x2 pdr AA pom poms (2x4), 20x20mm AA (6x2 + 8x1) guns, 6x21” TT (2x3).

The Modified Dido or Bellona Class were redesigned with just four 5.25” turrets, upgraded and radar-guided, and a much lower superstructure to improve stability. Their role was also somewhat different to the main class in that they were intended to be escort ships for carrier task forces and also act as picket ships for amphibious operations. Their armament comprised 8x5.25” DP guns (2x4), 12x2 pdrs AA (3x4) guns, 12x20mm AA (6x2) guns and 6x21” TT (2x3).

Interestingly, although designed as trade protection cruisers or carrier escorts, in the Mediterranean the Didos and Bellonas were often used as fleet cruisers (with the Arethusas), participating, for example, in the Battle of Cape Matapan and the Second Battle of Sirte where they successfully held off larger and more powerful Italian cruisers. They were also at the Allied Invasion of North Africa, Salerno, D-Day and Okinawa. Their action-packed lives inevitably led to high losses, six being lost in WWII. So highly thought of was the class that, with the outbreak of the Korean war, there was a scheme to replace the 5.25” turrets with four or five automatic, radar-controlled, twin 3” AA turrets with an extremely high rate of fire but in the event it was found too difficult (and costly) to fit-in all the necessary equipment into a relatively small hull. The survivors were scrapped in 1955-68, although one sold to Pakistan survived until 1985.

HMS Scylla herself was built by Scotts Shipbuilding, Greenock, being launched in 1940 and completed in 1942. She had a very active service in WWII including escorting Russian convoys, taking part in the North African Landings, sinking the German blockade runner Rhakotis and taking part in the 1943 Salerno Landings as part of the Support Carrier Force. After that the Scylla was refitted as an Escort Carrier Flagship with the innovation of an Action Information Centre (AIO) – as was the Modified Dido HMS Royalist – to coordinate radar and interception information.

Because of this highly valuable capability, the Scylla was made the RN flagship at the Normandy landings, co-ordinating all RN shipping and warship movements but particularly RN MTB’s and MGB’s defending the Eastern Task Force against attacking German E-Boats. However, on 23 June Scylla hit a mine; she survived and was towed back to Portsmouth only to be found to be so seriously damaged that she was declared a constructive total loss, She was then used as a target until 1950 when she was scrapped.