The British Royal Navy operated large numbers of small Motor Minesweepers (MMS) during the Second World War, in two major classes: the first with 105 ft (32 m) hulls (of which 294 were built) and the second with 126 ft (38 m) hulls (of which 102 were built).

Intended to counter magnetic influence mines in coastal waters, they had wooden hulls.

In the early months of the Second World War, Germany made extensive use of magnetic mines, which led to a requirement for a wooden minesweeper, less vulnerable than steel trawlers.

[3][4] They were powered by a 500 bhp (370 kW) diesel engine, giving a speed of 11 kn (13 mph; 20 km/h).

Pulsing a high current through the cables generated a magnetic field sufficient to set off mines over an area of about 1 acre (0.40 ha).

[5] The coastal minesweepers had pennant numbers MMS-1 to MMS-118, MMS-123 to MMS-313 and MMS-1001 to MMS-1090, the last group measuring 126 feet between perpendiculars.

[8] Ten had been built for the Royal Canadian Navy, Coquitlam, Crankbrook, Daerwood, Kalamalka, La Vallée, Llewellyn, Lloyd George, Revelstoke, Rossland and St. Joseph.

[15][16] Eleven were transferred to the Royal Netherlands Navy; two were lost, one returned to the RN, and eight were retained postwar.

Seven were in use as tenders to RNVR divisions: Bernicia (ex-MMS-1090), Curzon (ex-MMS-1017), Graham (ex-MMS-1045), hUMBER (EX-mms-1030), Kilmorey (ex-MMS-1034), Mersey (ex-MMS-1075) and Montrose (ex-MMS-1077).

All were returned to the RN for disposal in October 1947[23] Eight were transferred to the Royal Netherlands Navy: Duiveland (ex-MMS-1044), Ijselmond (ex-MMS-1026), Overflakee (ex-MMS-1046), Schokland (ex-MMS-1082), Tholen (ex-MMS-1014), Voorne (ex-MMS-1043), Wieringen (ex-MMS-1025) and Walcheren (ex-MMS-1042)[24][19] MMS-1085 and 1086 were transferred to the Royal Norwegian Navy, where they were named Orka and Vefsna, respectively They were retained postwar.