The Castle-class corvette was a stretched version of the preceding, enlarged to improve seakeeping and to accommodate modern weapons. The ships displaced 1010LT at standard load and 1510LT at deep load. They had an overall length of 252feet, a beam of 36feet and a deep draught of 14feet. They were powered by a pair of triple-expansion steam engines, each driving one propeller shaft using steam provided by two Admiralty three-drum boilers. The engines developed a total of 2880ihp and gave a maximum speed of 16.5kn. The Castles carried enough fuel oil to give them a range of 6500nmi at . The ships' complement was 99 officers and ratings.[1]
The Castle-class ships were equipped with a single QF 4adj=onNaNadj=on Mk XVI gun forward, but their primary weapon was their single three-barrel Squid anti-submarine mortar. This was backed up by one depth charge rail and two throwers for 15 depth charges. The ships were fitted with two twin and a pair of single mounts for 20mm Oerlikon light AA guns.[2] Provision was made for a further four single mounts if needed. They were equipped with Type 145Q and Type 147B ASDIC sets to detect submarines by reflections from sound waves beamed into the water. A Type 277 search radar and a HF/DF radio direction finder rounded out the Castles' sensor suite.[3]
Denbigh Castle, the only ship of her name to serve in the Royal Navy,[4] was ordered on 19 December 1942 and laid down by John Lewis & Sons at their shipyard in Aberdeen, Scotland, on 30 September 1943. The ship was launched on 5 August 1944 and completed on 30 December 1944. She arrived at Tobermory, Mull, Scotland, on 12 January 1945 to begin training at the Royal Navy's Anti-Submarine Training School, . Having completed training, Denbigh Castle arrived at Scapa Flow on 29 January to join the 7th Escort Group.[5]
Commanded by Lieutenant Commander Graham Butcher, the ship escorted Convoy JW 64 to Murmansk at the beginning of February. On the 7th, Denbigh Castle claimed to have shot down a German torpedo bomber.[6] Almost a week later, the ship was torpedoed by U-992 as the convoy entered the Kola Inlet[7] at 00:13 on 13 February; the corvette's radar had picked up the submarine at a range of, but had not identified her due to the confused radar returns and darkness. The torpedo struck the bow and the crew thought that the ship had struck a mine. The explosion killed eleven ratings and threw the four-inch gun onto the Squid platform behind it. The remaining bow structure sagged downwards, although Denbigh Castle was in no danger of sinking. The destroyer transferred her medical officer over and the corvette came alongside around 00:45 to receive casualties, and Butcher ordered as many ratings aboard her as he thought he could spare. Bluebell began towing Denbigh Castle at 02:05 and reached a maximum speed of, Serapis screening the ships during the tow.[8]
The came alongside at 04:30 to transfer a 100t salvage pump as the corvette was still taking on water. At 05:01, Butcher ordered all remaining hands aboard the Soviet ship because Denbigh Castle was slowly sinking by the bow, only the officers remaining aboard. Buresvestniks captain, not wanting the corvette to founder in the channel, took over the tow at 06:15, by which time her stern was nearly out of the water. Denbigh Castle was beached at 07:30 at Bolshaya Volokovaya Bay near Vaenga; Buresvestnik then pushed her stern around. The ship began to slowly list with the ebbing tide and the officers abandoned her at 09:05; five minutes later she capsized and slid into deeper water. The intense cold made later efforts to retrieve or destroy secret documents and equipment still aboard extremely difficult, but the diving team from the light cruiser did manage to demolish the radar office. In recognition of her service, Denbigh Castle was awarded the battle honour Arctic 1945.[9]