# Castle-class corvette

The Castle-class corvette was an ocean going convoy escort developed by the United Kingdom during the Second World War. It was the follow-on to the Flower-class corvette, and designed to be built in shipyards that were producing the Flowers. The Castle-class was a general improvement over the smaller Flowers which were designed for coastal rather than open ocean use.
The Castle-class corvettes started appearing in service during late 1943.

## Background

In mid-1939, the Admiralty ordered 175 Flower-class corvettes for protecting shipping on the east coast of Britain. They were designed to be built in large numbers in small shipyards without propulsion and other components (mainly gearboxes, but also guns) then in short supply so not compete with other warships for construction. By the time the Flowers began entering service in late-1940, due to their long range they were required to undertake missions beyond coastal waters. The Flowers were unsuited for open-ocean escort missions in the North Atlantic, especially in poor weather; they lacked speed, endurance, and habitability but became the mainstay of the Mid-Ocean Escort Force protecting convoys crossing the Atlantic.
The Royal Navy recognized the limitations of the Flower and began designing an open-ocean escort in November 1940, which became the River-class frigate. The larger Rivers were too expensive to produce at the required rate and needed larger slipways. In response, the Loch-class frigate was developed in late-1942, which was developed from the River and designed for prefabricated construction. The Castle was developed from a proposal by Smith's Dock Company – who had designed the Flower-class – for a stretched Flower. The result was a scaled-down version of the Loch for shipyards that only built corvettes using mainly traditional methods.
The design was approved in May 1943 and 96 Castles were ordered from yards in the UK and Canada. Fifteen British and all 37 Canadian ships were later cancelled; Canada receiving twelve British-built ships instead. The UK completed a further five as convoy rescue ships for its Merchant Navy. Four became weather ships after the war.

## Design

The Castle resembled later Flowers with an extended forecastle and mast behind the bridge, but was 135 tons heavier and 47 feet longer. The Admiralty Experiment Works at Haslar developed an improved hull form which, in combination with the increased length, made the Castle at least half a knot faster than the Flower despite using the same engine. The Castle also had a single-screw. A lattice mainmast was used instead of the pole version fitted to the Flowers.
Construction used mainly traditional methods with as much welding as possible. Scantling was based on the Flower, but lightened in some areas. The wireless office (the same as on the Loch), the radar office, and the lattice mast were installed as prefabricated units.
The Castle was armed with a Squid anti-submarine mortar, directed by Type 145 and 147B ASDIC. The Flower used the older Hedgehog mortar and could not be fitted with Squid. The first operational Type 147 and Squid were installed aboard HMS Hadleigh Castle in September 1943.
In place of the BL 4-inch Mk IX main gun, the Castles had the new QF 4-inch Mk XIX gun on a High-Angle/Low-Angle mounting which could be used against aircraft as well as surface targets such as submarines.

## In service

The Castle was criticized for being barely fast enough to fight German Type VII submarines and difficult to handle at low speed.

## Ships
### 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)
* HMCS Bowmanville (K493) (ex-HMS Nunney Castle), sold to Republic of China as cargo ship, but taken over by the Communist People's Liberation Army Navy after the end of the Chinese Civil War and rearmed with Soviet guns, entering PLAN service as Guangzhou.
* HMCS Copper Cliff (K495) (ex-HMS Hever Castle)
* HMCS Hespeler (K489) (ex-HMS Guildford Castle) (later SS Chilcotin)
* HMCS Humberstone (K497) (ex-HMS Norham Castle)
* HMCS Huntsville (K499) (ex-HMS Woolvesey Castle)
* HMCS Kincardine (K490) (ex-HMS Tamworth Castle)
* HMCS Leaside (K492) (ex-HMS Walmer Castle, later SS Coquitlam II)
* HMCS Orangeville (K491) (ex-HMS Hedingham Castle), sold to Republic of China as cargo ship, but taken over by the ROC Navy on 29 June 1950 and rearmed with US guns, entering ROCN service as De An (德安)
* HMCS Petrolia (K498) (ex-HMS Sherborne Castle)
* HMCS St. Thomas (K488) (ex-HMS Sandgate Castle, later SS Camosun III)
* HMCS Tillsonburg (K496) (ex-HMS Pembroke Castle), sold to Republic of China as cargo ship, but taken over by ROCN on 29 June 1950 and rearmed with US guns, entering ROCN service as Kao An (高安)

### Royal Navy

The first of the Castle-class were the prototypes Hadleigh Castle and Kenilworth Castle, ordered on 9 December 1942; another 12 vessels were also ordered on 9 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) were cancelled late in 1943.
Castle-class corvettes of the Royal Navy :
| Name | Pennant | Hull builder | Ordered | Laid down | Launched | Commissioned | Paid off | Fate |
| Hadleigh Castle | K355 | Smiths Dock Company | 9 Dec 1942 | 4 Apr 1943 | 21 Jun 1943 | 18 Sep 1943 | Aug 1946 | Scrapped, Jan 1959 |
| Kenilworth Castle | K420 | Smiths Dock Company | 9 Dec 1942 | 7 May 1943 | 17 Aug 1943 | 22 Nov 1943 | 1948 | Scrapped, 20 Jun 1959 |
| Allington Castle | K689 | Fleming & Ferguson | 9 Dec 1942 $^{(a)}$ | 22 Jul 1943 | 29 Feb 1944 | 19 June 1944 | 1947 | Scrapped 1958 |
| Bamborough Castle | K412 | John Lewis & Co. Ltd | 9 Dec 1942 | 1 Jul 1943 | 11 Jan 1944 | 30 May 1944 | 1950 | Scrapped 22 May 1959 |
| Caistor Castle | K690 | John Lewis & Co. Ltd | 9 Dec 1942 | 26 Aug 1943 | 22 May 1944 | 29 September 1944 | 1947 | Scrapped Mar 1956 |
| Denbigh Castle | K696 | John Lewis & Co. Ltd | 9 Dec 1942 | 30 Sep 1943 | 5 Aug 1944 | 30 December 1944 | | Declared constructive total loss, 13 Feb 1945 |
| Farnham Castle | K413 | John Crown & Sons Ltd | 9 Dec 1942 | 25 Jun 1943 | 25 Apr 1944 | 31 Jan 1945 | 1947 | Scrapped, 31 Oct 1960 |
| Hedingham Castle | K529 | John Crown & Sons Ltd | 9 Dec 1942 | 2 Nov 1943 | 30 Oct 1944 | 12 May 1945 | Aug 1945 | Scrapped, Apr 1958 |
| Lancaster Castle | K691 | Fleming & Ferguson | 9 Dec 1942 | 10 Sep 1943 | 14 Apr 1944 | 15 Sep 1944 | 1947 | Scrapped, 20 Jun 1959 |
| Maiden Castle | K443 | Fleming & Ferguson | 9 Dec 1942 | 1943 | 8 Jun 1944 | November 1944 | | Became convoy rescue ship Empire Lifeguard before completion; Scrapped, 22 Jul 1955 |
| Norham Castle (ex-Totnes Castle) | K447 | A. & J. Inglis | 9 Dec 1942 | 30 Sep 1943 | 12 Apr 1944 | 6 Sep 1944 | | Transferred to Canada as HMCS Humberstone 1944; Sold for mercantile service 1947 |
| Oakham Castle | K530 | A. & J. Inglis | 9 Dec 1942 | 30 Sep 1943 | 20 Jul 1944 | 10 Dec 1944 | 1950 | Became the weather ship Weather Reporter 1957 |
| Pembroke Castle | K450 | Ferguson Shipbuilders | 9 Dec 1942 | 3 Jun 1943 | 12 Feb 1944 | 29 June 1944 | | Transferred to Canada as HMCS Tillsonburg in 1944; Sold for mercantile service 1947; Sold to Republic of China as Kao An 1952 |
| Rayleigh Castle | K695 | Ferguson Shipbuilders | 9 Dec 1942 | 1943 | 12 Jun 1944 | Oct 1944 | | Completed as convoy rescue ship Empire Rest |
| Alnwick Castle | K405 | George Brown & Co. | 19 Jan 1943 | 1943 | 3 Oct 1944 | | 1957 | Broken up Dec 1958 |
| Barnard Castle | K594 | George Brown & Co. | | 1943 | 3 Oct 1944 | | | completed 1945 as convoy rescue ship Empire Shelter |
| Flint Castle | K383 | Henry Robb, at Leith | | 20 Apr 1943 | 1 Sep 1943 | 31 Dec 1943 | Mar 1956 | Broken up 10 Jul 1958 |
| Guildford Castle | K378 | Henry Robb, at Leith | | 25 May 1943 | 13 Nov 1943 | 11 Mar 1944 | | to Canada as HMCS Hespeler, 1944; Sold for mercantile service 1946 (later SS Chilcotin) |
| Hedingham Castle | K491 | Henry Robb, at Leith | | 23 Jul 1943 | 26 Jan 1944 | 10 May 1944 | | to Canada as HMCS Orangeville, 1944; Sold for mercantile service 1947; to Republic of China Navy 1951 as Te An |
| Knaresborough Castle | K389 | Blyth Dry Dock | | 22 Apr 1943 | 1 Sep 1943 | 5 April 1944 | 1947 | Broken up 16 Mar 1956 |
| Launceston Castle | K397 | Blyth Dry Dock | | 27 May 1943 | 27 Nov 1943 | 20 June 1944 | 1947 | Broken up 3 Aug 1959 |
| Sandgate Castle | K473 | Smiths Dock, at Middlesbrough | | 23 Jun 1943 | 28 Dec 1943 | 18 May 1944 | 22 Nov 1945 | to Canada as HMCS St. Thomas, 1944; sold for mercantile service 1946 (later SS Camosun III) |
| Tamworth Castle | K393 | Smiths Dock, at Middlesbrough | | 25 Aug 1943 | 26 Jan 1944 | 3 Jul 1944 | 17 Feb 1946 | to Canada as HMCS Kincardine; sold for mercantile service 1946 |
| Walmer Castle | K405 | Smiths Dock, at Middlesbrough | | 23 Sep 1943 | 10 Mar 1944 | 5 Sep 1944 | 16 Nov 1945 | to Canada as HMCS Leaside; sold for mercantile service 1946 (later SS Coquitlam II) |
| York Castle | | Ferguson Brothers, Port Glasgow | | 1944 | 20 Sep 1944 | | | completed Feb 1945 as convoy rescue ship SS Empire Comfort |
| Hever Castle | | Blyth Dry Dock | | 29 June 1943 | 24 Feb 1944 | 15 Aug 1944 | | to Canada as HMCS Copper Cliff, 1944; Sold for mercantile service 1947, then became Chinese (People's Liberation Army) 1949 |
| Leeds Castle | K384 | William Pickersgill & Sons | 23 Jan 1943 | 22 Apr 1943 | 12 Oct 1943 | 15 Feb 1944 | Nov 1956 | broken up 5 Jun 1958 |
| Morpeth Castle | K693 | William Pickersgill & Sons | 23 Jan 1943 | 23 Jun 1943 | 26 Nov 1943 | 13 Jul 1944 | 1946 | broken up 9 Aug 1960 |
| Nunney Castle | K446 | William Pickersgill & Sons | 23 Jan 1943 | 12 Aug 1943 | 26 Jan 1944 | 8 Oct 1944 | | to Canada as HMCS Bowmanville, 1944; Sold for mercantile service 1946, then became Chinese (People's Liberation Army) Kuang Chou 1949 |
| Oxford Castle | K692 | Harland and Wolff | 23 Jan 1943 | 21 Jun 1943 | 11 Dec 1943 | 10 Mar 1944 | 1946 | broken up 6 Sep 1960 |
| Pevensey Castle | K449 | Harland and Wolff | 23 Jan 1943 | 21 Jun 1943 | 11 Jan 1944 | 10 Jun 1944 | Feb 1946 | Became weather ship Weather Monitor in 1959 |
| Rising Castle | K398 | Harland and Wolff | 23 Jan 1943 | 21 Jun 1943 | 8 Feb 1944 | 26 Jun 1944 | 14 Mar 1946 | to Canada as HMCS Arnprior, 1944; transferred to Uruguay as Montevideo |
| Scarborough Castle | K536 | Fleming & Ferguson | 23 Jan 1943 | 1944 | 8 Sep 1944 | Jan 1945 | | Completed as convoy rescue ship (Empire Peacemaker) |
| Sherborne Castle | K453 | Harland and Wolff | 23 Jan 1943 | 21 June 1943 | 24 Feb 1944 | 14 Jul 1944 | 8 Mar 1946 | to Canada as HMCS Petrolia, 1944; Sold for mercantile service 1946 |
| Tintagel Castle | K399 | Ailsa Shipbuilding Company | 23 Jan 1943 | 29 April 1943 | 13 Dec 1943 | 7 Apr 1944 | Aug 1956 | Broken up Jun 1958 |
| Wolvesey Castle | K461 | Ailsa Shipbuilding Company | 23 Jan 1943 | 1 Jun 1943 | 24 Feb 1944 | 15 Jun 1944 | 15 Feb 1946 | to Canada as HMCS Huntsville, 1944; Sold for mercantile service 1947 |
| Amberley Castle | K386 | S P Austin & Son Ltd | 2 Feb 1943 | 31 May 1943 | 25 Nov 1943 | 24 Nov 1944 | 1947 | Became the weather ship Weather Adviser in 1960 |
| Berkeley Castle | K387 | Barclay Curle | 2 Feb 1943 | 23 Apr 1943 | 19 Aug 1943 | 18 Nov 1944 | 1946 | Scrapped 24 February 1956 |
| Carisbrooke Castle | K379 | Caledon Shipbuilding & Engineering Company | 2 Feb 1943 | 12 Mar 1943 | 31 Jul 1943 | 17 Nov 1943 | 1947 | Scrapped 14 June 1958 |
| Dumbarton Castle | K388 | Caledon Shipbuilding & Engineering Company | 2 Feb 1943 | 6 May 1943 | 28 Sep 1943 | 25 Feb 1944 | 1947 | Scrapped March 1961 |
| Hurst Castle | K416 | Caledon Shipbuilding & Engineering Company | 2 Feb 1943 | 6 August 1943 | 23 Feb 1944 | 9 Jun 1944 | | Sunk by U-482 on 1 Sep 1944 |
| Portchester Castle | K362 | Swan Hunter | 6 Feb 1943 | 17 March 1943 | 21 Jun 1943 | 8 Nov 1943 | 1947 | Scrapped 14 May 1958 |
| Rushen Castle | K372 | Swan Hunter | 6 Feb 1943 | 8 April 1943 | 16 Jul 1943 | 24 Feb 1944 | 1946 | Became the weather ship Weather Surveyor in 1960 |
| Shrewsbury Castle | K374 | Swan Hunter | 6 Feb 1943 | 5 May 1943 | 16 Aug 1943 | 24 Apr 1944 | | Transferred to Norway on completion and renamed HNoMS Tunsberg Castle; Sunk by mine 12 Dec 1944 |
Notes: (a) from the previous order placed for a Modified Flower-class corvette named Amaryllis.
Two of those 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 – HMS Shrewsbury Castle was loaned to the Royal Norwegian navy on 17 April 1944. On 12 December 1944, she hit a mine and sank.

## Cancelled

Fifteen 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.
The following 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
* Dhyfe 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

* Hurst Castle was sunk by U-482 northwest of Ireland on 1 September 1944.
* HNoMS Tunsberg Castle was sunk by a mine near Båtsfjord, Norway on 12 December 1944.
* Denbigh Castle was hit by a torpedo from U-992 in the Barents Sea on 13 February 1945. She was towed by Bluebell to the Kola Inlet but later capsized.

## U-boats sunk by Castles

* U-744 was sunk by Icarus, St. Catharines, Fennel, Chilliwack, Chaudiere, Gatineau and Kenilworth Castle on 6 March 1944
* U-484 was sunk in the north-west of Ireland by Portchester Castle and Helmsdale on 9 September 1944
* U-1200 was sunk south of Ireland by Pevensey Castle, Lancaster Castle, Portchester Castle and Kenilworth Castle on 11 November 1944
* U-387 was sunk in the Barents Sea by Bamborough Castle on 9 December 1944
* U-877 was sunk north-west of the Azores by St. Thomas on 27 December 1944
* U-425 was sunk in the Barents Sea by Lark and Alnwick Castle on 17 February 1945
* U-878 was sunk in the Bay of Biscay by Vanquisher and Tintagel Castle 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 Portchester Castle).

## 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. 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