The Fairmile B type superseded the original Fairmile A type, which had been designed by Norman Hart.
First batch (September 1939 orders) An initial batch of 24 of these (
ML 101 to
ML 124) was ordered by the Admiralty as part of its first emergency war programme on 22 September 1939 from the
Fairmile Marine company, of which the first eleven (plus the prototype
ML 100) were completed to the Hart design (see
Fairmile A motor launch); the remaining thirteen (
ML 112 to
ML 124) were completed to the new Fairmile B design. The first Fairmile B motor launch (actually
ML 113 from Tough Bros,
Teddington) was completed and delivered on 12 August 1940, with a further eleven from this first production batch entering service before the end of the year (the last of the batch to be completed -
ML 123 - was delayed until 1941).
Second batch (January 1940 orders) The Admiralty placed a massive order for a second batch of Fairmile Bs - 120 vessels in total - on 8 January 1940. These were numbered
ML 125 to
ML 244. Of these, 37 were delivered by the end of 1940, another 77 during the first half of 1941, and the last 6 during the second half of 1941.
Third batch (May 1940 orders) An order for a third batch, this time of 65 boats, was placed on 21 May 1940; these were numbered
ML 245 to
ML 309, and were all delivered during 1941, as were two extra units (
ML 310 and
ML 311) ordered on 28 June 1940 for Singapore to be assembled by the Singapore Harbour Board; this last pair were delivered to Singapore on 29 November 1941, only to be lost in February 1942 to the Japanese (who re-used
ML 310 under the name
Suikei 12).
Fourth batch (August 1940 orders) The fourth batch of 24 boats was ordered on 28 July 1940 as
ML 312 to
ML 335. However, these were altered to be completed instead as Motor Gunboats, re-classed as
Fairmile C motor gun boats, and the prefixes to their numbers changed from "ML" to "MGB", retaining the same numbers. In their place, a new batch of 120 Fairmile B boats was ordered under the 1940 Supplemental Programme, 76 to be assembled in the UK and 44 abroad. Most were ordered on 21 August, with 6 further boats ordered 6 days later; these became
ML 336 to
ML 455. The first 12 (
ML 336 to
ML 347) were for assembly in UK boatyards, the next 14 (
ML 348 to
ML 361) for assembly at Cairo, the next four for assembly by the Singapore Harbour Board (
ML 362 to
ML 365), two for assembly at Dar es Salaam (
ML 366 and
ML 367), two at Bermuda for the Royal Canadian Navy (
ML 368 and
ML 369), two in Jamaica for Caribbean service (
ML 370 and
ML 371, also on 27 August), four at Singapore (
ML 372 to
ML 377, although four of these were destroyed on the stocks in January 1942, while the last pair was switched to Bombay Dockyard on 22 February 1942 following the fall of Singapore). Thirty-two units (
ML 392 to
ML 423 ) were ordered for Commonwealth forces, for assembly overseas. Eight units were ordered as
ML 392 to
ML 399 on 12 August 1941 for assembly in Canada (although these were all passed on to the United States Navy); twenty more units were ordered on 4 September 1941, twelve for assembly in New Zealand boatyards for the Royal New Zealand Navy (
ML 400 to
ML 411) and eight for assembly in Indian boatyards for the Royal Indian Navy (
ML 412 to
ML 419); and four more were ordered for assembly in Singapore, of which two (
ML 420 and
ML 421) were re-ordered on 12 January 1942, and two (
ML 422 and
ML 423) were re-ordered on 28 November 1941.
Fifth batch (1941 Programme orders) Forty boats were ordered on 27 August 1941. The first twenty-three of these (
ML 478 to
ML 500) were for the Royal Navy, while seventeen (
RML 511 to
RML 527) were rescue launches for the Royal Air Force (the numbers 501 to 510 were allocated to large MTBs). An additional forty-eight boats were ordered on 28 November 1941 under a 1941 Supplementary Programme. Twenty-six of these were rescue launches for the RAF (
RML 528 to
RML 553) while another twenty-two boats (
ML 554 to
ML 575) were also ordered for the Navy.
Sixth batch (1942 orders) Further batches followed, producing
ML 576 onwards, many assembled in Overseas yards, with a final total of about 650 boats of this Type eventually assembly worldwide, including 60 in Canada. Twenty-five more boats (
ML 576 to
ML 600) were ordered on 18 May 1942. All boats were essentially the same, although they could be adapted to serve in several roles by the expedient of having pre-drilled rails on their decks spaced to allow the fitting of various types of armaments. Although their armament initially reflected their main anti-submarine mission, nine of them were fitted with
torpedo tubes taken from ex-US
Town-class destroyers; they formed the 2nd ML Flotilla tasked with anti-invasion duty, until the threat had passed. ==Service==