Castle-class corvette

The Castle-class corvettes were an updated version of the much more numerous Flower-class corvettes of the Royal Navy, and started appearing during late 1943. They were equipped with radar as well as asdic.

Design
The Admiralty had decided to cease Flower-class construction in favour of the larger River-class frigates as the Flower-class had originally been intended for coastal escort work and were not entirely satisfactory for Atlantic convoy service. In particular, they were slow, poorly armed, and rolled badly in rough seas which quickly exhausted their crews. However, many shipyards were not large enough to build frigates. The Castle-class was designed to be built on small slipways for about half the overall effort of a Loch-class frigate. The Loch was a River built using the "American system" of prefabrication.

Appearance was much like the later "long forecastle" variant of the Flowers and they were a little larger (around 1,200 tons – about 200 tons more than the Flowers, and 40 ft (12 m) longer).

The most obvious difference was the lattice mainmast instead of the pole one fitted to the Flowers. There was also a more "square cut" look to the stern although it was still essentially a cruiser spoon type, this difference was only visible from abaft the beam.

Armament was similar except that the depth charge fitment had been replaced by one for the Squid anti-submarine mortar. HMS Hadleigh Castle received the first production Squid mounting.

Propulsion machinery was identical to the Flowers, and experienced officers felt that they were seriously under powered, having a tendency to turn into the wind despite everything the helmsman could do. The fact that Squid attacks required a fairly low speed (compared to depth charge attacks) only made matters worse.

Most had been scrapped by the end of the 1950s, but a few survived a little longer as weather ships. However, the last was the Uruguayan Montevideo, originally HMS Rising Castle (K398) and scrapped in 1975.

Most were operated by the Royal Navy, but twelve were assigned to the Royal Canadian Navy and one to the Royal Norwegian Navy. Three Castles were sunk through enemy action, and Castles participated in the sinking of seven U-boats.

Royal Canadian Navy
The following vessels were all originally built for the Royal Navy, but were transferred to the RCN on completion (for details of builders and construction dates see under Royal Navy below). All their pennant numbers (except Hedingham Castle, which was never completed), as well as their names, were changed when transferred.
 * HMCS Arnprior (K494) (ex-HMS Rising Castle (K398))
 * HMCS Bowmanville (K493) (ex-HMS Nunney Castle (K446))
 * HMCS Copper Cliff (K495) (ex-HMS Hever Castle (K521))
 * HMCS Hespeler (K489) (ex-HMS Guildford Castle (K378)) (later SS Chilcotin)
 * HMCS Humberstone (K497) (ex-HMS Norham Castle (K447))
 * HMCS Huntsville (K499) (ex-HMS Wolvesey Castle (K461))
 * HMCS Kincardine (K490) (ex-HMS Tamworth Castle (K393))
 * HMCS Leaside (K492) (ex-HMS Walmer Castle (K405), later SS Coquitlam II)
 * HMCS Orangeville (K491) (ex-HMS Hedingham Castle (K491))
 * HMCS Petrolia (K498) (ex-HMS Sherborne Castle (K453))
 * HMCS St. Thomas (K488) (ex-HMS Sandgate Castle (K473), later SS Camosun III)
 * HMCS Tillsonburg (K496) (ex-HMS Pembroke Castle (K450))

Royal Navy
The initial Castle was the Allington Castle, re-ordered on 9 December 1942 (from the previous order placed for a Modified Flower-class corvette named Amaryllis); another 13 vessels were ordered on 19 December, also under the 1942 War Programme.

The remaining eighty-one ships were all ordered for the RN under the 1943 War Programme, of which thirty were completed. Fifty-one of these ships (15 from UK shipyards and 36 from Canadian shipyards) which were cancelled late in 1943 are shown separately below.

Fourteen ordered 19 January 1943, of which 3 were cancelled:
 * HMS Alnwick Castle (K405), built by George Brown, at Greenock; begun 12 June 1943, launched 23 May 1944 and completed 11 November 1944. Paid off 1957 and broken up December 1958.
 * HMS Barnard Castle (K594), built by George Brown, at Greenock; begun 1943, launched 3 October 1944 and completed 1945 as convoy rescue ship Empire Shelter.
 * HMS Flint Castle (K383), built by Henry Robb, at Leith; begun 20 April 1943, launched 1 September 1943 and completed 31 December 1943. Paid off March 1956 and broken up 10 July 1958.
 * HMS Guildford Castle (K378), built by Henry Robb, at Leith; begun 25 May 1943, launched 13 November 1943 and completed 11 March 1944; to Canada as HMCS Hespeler, 1944. Sold for mercantile service 1946 (later SS Chilcotin)
 * HMS Hedingham Castle (K491), built by Henry Robb, at Leith; begun 23 July 1943, launched 26 January 1944 and completed 10 May 1944; to Canada as HMCS Orangeville, 1944. Sold for mercantile service 1947; to Republic of China Navy 1951 as Te An.
 * HMS Knaresborough Castle (K389), built by Blyth Dry Dock; begun 22 April 1943, launched 1 September 1943 and completed 5 April 1944. Paid off 1947 and broken up 16 March 1956.
 * HMS Launceston Castle (K397), built by Blyth Dry Dock; begun 27 May 1943, launched 27 November 1943 and completed 20 June 1944. Paid off 1947 and broken up 3 August 1959.
 * HMS Sandgate Castle (K473), built by Smiths Dock, at Middlesbrough; begun 23 June 1943, launched 28 December 1943 and completed 18 May 1944; to Canada as HMCS St. Thomas, 1944. Paid off 22 November 1945 and sold for mercantile service 1946 (later SS Camosun III).
 * HMS Tamworth Castle (K393) built by Smiths Dock, at Middlesbrough; begun 25 August 1943, launched 26 January 1944 and completed 3 July 1944; to Canada as HMCS Kincardine. Paid off 17 February 1946 and sold for mercantile service 1946.
 * HMS Walmer Castle (K460), built by Smiths Dock, at Middlesbrough; begun 23 September 1943, launched 10 March 1944 and completed 5 September 1944; to Canada as HMCS Leaside. Paid off 16 November 1945 and sold for mercantile service 1946 (later SS Coquitlam II).
 * York Castle, built by Ferguson Brothers, at Port Glasgow; begun 1944, launched 20 September 1944 and completed February 1945 as convoy rescue ship SS Empire Comfort.

Sixteen ordered 23 January 1943, of which five were cancelled:
 * HMS Hever Castle (K521), built by Blyth Dry Dock; begun 29 June 1943, launched 24 February 1944 and completed 15 August 1944; to Canada as HMCS Copper Cliff, 1944. Sold for mercantile service 1947, then became Chinese (People's Liberation Army) 1949.
 * HMS Leeds Castle (K384), built by William Pickergill, at Sunderland; begun 22 April 1943, launched 12 October 1943 and completed 15 February 1944. Paid off November 1956 and broken up 5 June 1958.
 * HMS Morpeth Castle (K693), built by William Pickergill, at Sunderland; begun 23 June 1943, launched 26 November 1943 and completed 13 July 1944. Paid off 1946 and broken up 9 August 1960.
 * HMS Nunney Castle (K446), built by William Pickergill, at Sunderland; begun 12 August 1943, launched 26 January 1944 and completed 8 October 1944; to Canada as HMCS Bowmanville, 1944. Sold for mercantile service 1946, then became Chinese (People's Liberation Army) Kuang Chou 1949.
 * HMS Oxford Castle (K692), built by Harland and Wolff, at Belfast; begun 21 June 1943, launched 11 December 1943 and completed 10 March 1944. Paid off 1946 and broken up 6 September 1960.
 * HMS Pevensey Castle (K449), built by Harland and Wolff, at Belfast; begun 21 June 1943, launched 11 January 1944 and completed 10 June 1944. Paid off February 1946 and became weather ship Weather Monitor in 1959.
 * HMS Rising Castle (K398), built by Harland and Wolff, at Belfast; begun 21 June 1943, launched 8 February 1944 and completed 26 June 1944; to Canada as HMCS Arnprior, 1944. Paid off 14 March 1946 and transferred to Uruguay as Montevideo.
 * HMS Scarborough Castle (K536), built by Fleming & Ferguson, at Paisley; begun 1944, launched 8 September 1944 and completed January 1945 as convoy rescue ship Empire Peacemaker)
 * HMS Sherborne Castle (K453), built by Harland and Wolff, at Belfast; begun 21 June 1943, launched 24 February 1944 and completed 14 July 1944; to Canada as HMCS Petrolia, 1944. Paid off 8 March 1946 and sold for mercantile service 1946.
 * HMS Tintagel Castle (K399), built by Ailsa, at Troon; begun 29 April 1943, launched 13 December 1943 and completed 7 April 1944. Paid off August 1956 and broken up June 1958.
 * HMS Wolvesey Castle (K461), built by Ailsa, at Troon; begun 1 June 1943, launched 24 February 1944 and completed 15 June 1944; to Canada as HMCS Huntsville, 1944. Paid off 15 February 1946 and sold for mercantile service 1947.

Five ordered 2 February 1943:

Three ordered 6 February 1943:

Two ordered 3 March 1943, three ordered 4 May 1943 and two ordered 10 July 1943 were all cancelled, as were all thirty-six ordered from Canadian shipyards on 15 March 1943.

Royal Norwegian Navy

 * HNoMS Tunsberg Castle – (ex-HMS Shrewsbury Castle (K374), lost on 12 December 1944).

Cancelled
15 ships ordered for the Royal Navy from UK shipyards as part of the 1943 Programme were all cancelled on 31 October 1943:
 * Caldecot Castle – ordered 19 January 1943 from John Brown & Company, Clydebank.
 * Dover Castle – ordered 19 January 1943 from A. & J. Inglis, Glasgow.
 * Dudley Castle – ordered 19 January 1943 from A. & J. Inglis, Glasgow.
 * Bere Castle – ordered 23 January 1943 from John Brown & Company, Clydebank.
 * Calshot Castle – ordered 23 January 1943 from John Brown & Company, Clydebank.
 * Monmouth Castle (originally to have been Peel Castle) – ordered 23 January 1943 from John Lewis & Sons, Aberdeen.
 * Rhuddlan Castle – ordered 23 January 1943 from John Crown & Sons, Sunderland.
 * Thornbury Castle – ordered 23 January 1943 from Ferguson Brothers, Port Glasgow.
 * Appleby Castle – ordered 3 March 1943 from Austin, at Sunderland.
 * Tonbridge Castle – ordered 3 March 1943 from Austin, at Sunderland.
 * Norwich Castle – ordered 4 May 1943 from John Brown & Company, Clydebank.
 * Oswestry Castle – ordered 4 May 1943 from John Crown & Sons, Sunderland.
 * Pendennis Castle – ordered 4 May 1943 from John Crown & Sons, Sunderland.
 * Alton Castle – ordered 10 July 1943 from Fleming & Ferguson, Paisley.
 * Warkworth Castle – ordered 10 July 1943 from Fleming & Ferguson, Paisley.

36 ships were ordered on 15 March 1943 for the Royal Navy from Canadian shipyards for completion between May 1944 and June 1945, but were all cancelled in December 1943:


 * Aydon Castle
 * Barnwell Castle
 * Beeston Castle
 * Bodiam Castle
 * Bolton Castle
 * Bowes Castle
 * Bramber Castle
 * Bridgnorth Castle
 * Brough Castle
 * Canterbury Castle
 * Carew Castle
 * Chepstow Castle


 * Chester Castle
 * Christchurch Castle
 * Clare Castle
 * Clavering Castle
 * Clitheroe Castle
 * Clun Castle
 * Colchester Castle
 * Corfe Castle
 * Cornet Castle
 * Cowes Castle
 * Cowling Castle
 * Criccieth Castle


 * Cromer Castle
 * Devizes Castle
 * Dunster Castle
 * Egremont Castle
 * Fotheringay Castle
 * Helmsley Castle
 * Malling Castle
 * Malmesbury Castle
 * Raby Castle
 * Trematon Castle
 * Tutbury Castle
 * Wigmore Castle

Castles sunk or destroyed in action

 * HMS Hurst Castle (K416) was sunk by GERMAN SUBMARINE U-483 northwest of Ireland on 1 September 1944.
 * HNoMS Tunsberg Castle was sunk by a mine near Båtsfjord, Norway on 12 December 1944.
 * HMS Denbigh Castle (K696) was hit by a torpedo from GERMAN SUBMARINE U-992 in the Barents Sea on 13 February 1945. She was towed by HMS Bluebell (K80) to the Kola Inlet, but later capsized.

U-boats sunk by Castles

 * GERMAN SUBMARINE U-744 was sunk by HMS Icarus (D03), HMCS St. Catharines (K325), HMCS Fennel (K194), HMCS Chilliwack (K131), HMCS Chaudiere (H99), HMCS Gatineau (H61) and HMS Kenilworth Castle (K420) on 6 March 1944
 * GERMAN SUBMARINE U-484 was sunk in the north-west of Ireland by HMS Portchester Castle (K362) and HMS Helmsdale (K253) on 9 September 1944
 * GERMAN SUBMARINE U-1200 was sunk south of Ireland by HMS Pevensey Castle (K449), HMS Lancaster Castle (K691), HMS Portchester Castle (K362) and HMS Kenilworth Castle (K420) on 11 November 1944
 * GERMAN SUBMARINE U-387 was sunk in the Barents Sea by HMS Bamborough Castle (K412) on 9 December 1944
 * GERMAN SUBMARINE U-877 was sunk north-west of the Azores by HMCS St. Thomas (K488) on 27 December 1944
 * GERMAN SUBMARINE U-425 was sunk in the Barents Sea by HMS Lark (U11) and HMS Alnwick Castle (K405) on 17 February 1945
 * GERMAN SUBMARINE U-878 was sunk in the Bay of Biscay by HMS Vanquisher (D54) and HMS Tintagel Castle (K399) on 10 April 1945

Film appearance
The final third of the film The Cruel Sea is set on the Castle-class corvette Saltash Castle (portrayed by HMS Portchester Castle (K362)).

Post-war conversions
Three were converted to passenger/cargo ships for the Union Steamship Company of British Columbia, and were known as the White Boats (see Twigg). They were operated from 1946 to 1958, but were heavy on fuel and had limited cargo capacity, for example they could not carry cars in the hold.
 * SS Camosun III — ex-HMCS St. Thomas, HMS Sandgate Castle
 * SS Chilcotin — ex-HMCS Hespeler, HMS Guildford Castle
 * SS Coquitlam II — ex-HMCS Leaside, HMS Walmer Castle