HMS Alnwick Castle (K405)

The Castle-class corvette was a stretched version of the preceding Flower class, enlarged to improve seakeeping and to accommodate modern weapons. The ships displaced 1,010 long tons (1,030 t) at standard load and 1,510 long tons (1,530 t) at deep load. They had an overall length of 252 feet (76.8 m), a beam of 36 feet 9 inches (11.2 m) and a deep draught of 14 feet (4.3 m). 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 2,880 indicated horsepower (2,150 kW) and gave a maximum speed of 16.5 knots (30.6 km/h; 19.0 mph). The Castles carried enough fuel oil to give them a range of 6,500 nautical miles (12,000 km; 7,500 mi) at 15 knots (28 km/h; 17 mph). The ships' complement was 99 officers and ratings.^[1]

The Castle-class ships were equipped with a single QF 4-inch (102 mm) 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 20-millimetre (0.8 in) 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]

Alnwick Castle was laid down by George Brown & Co. at their shipyard at Greenock on 12 June 1943 and launched on 23 May 1944. She was completed on 11 November and served as a convoy escort until the end of the Second World War in May 1945.

On 17 February 1945, Alnwick Castle, Lt. Cdr. H.A. Stonehouse R.N.R., and HMS Lark used depth charges to sink German submarine U-425 near Murmansk.

Alnwick Castle was placed in reserve on 25 May and was sold for scrap in 1958.^[4] She arrived at Gateshead in December to be broken up.^[5]

• Chesneau, Roger, ed. (1980). Conway's All the World's Fighting Ships 1922–1946. Greenwich, UK: Conway Maritime Press. ISBN 0-85177-146-7.
• Colledge, J. J.; Warlow, Ben (2006) [1969]. Ships of the Royal Navy: The Complete Record of all Fighting Ships of the Royal Navy (Rev. ed.). London: Chatham Publishing. ISBN 978-1-86176-281-8.
• Goodwin, Norman (2007). Castle Class Corvettes: An Account of the Service of the Ships and of Their Ships' Companies. Liskeard, UK: Maritime Books. ISBN 978-1-904459-27-9.
• Lenton, H. T. (1998). British & Empire Warships of the Second World War. Annapolis, Maryland: Naval Institute Press. ISBN 1-55750-048-7.
• Rohwer, Jürgen (2005). Chronology of the War at Sea 1939–1945: The Naval History of World War Two (Third Revised ed.). Annapolis, Maryland: Naval Institute Press. ISBN 1-59114-119-2.