From Wiki:
The Fairmile D motor torpedo boat was a type of British Motor Torpedo Boat (MTB) designed by Bill Holt and conceived by Fairmile Marine for the Royal Navy. Nicknamed "Dog Boats", they were designed to combat the known advantages of the German E-boats over previous British coastal craft designs. They were bigger than earlier MTB or Motor Gun Boat (MGB) designs (which were typically around 70 feet) but slower, at 30 knots compared to 40 knots.
Unlike the Fairmile B designs, the Dog Boats were only produced in component form in Britain. Some were built for the RAF's Marine Branch for use in the long range air-sea rescue for downed airmen. 229 boats were built between 1942 and 1945.
Many versions were produced or converted from existing boats; MGB, MTB, MA/SB, LRRC and post-war FPB.
Since the Fairmile D could be fitted out with a mix of armament that gave it the capabilities of both a Motor Gun Boat and a Motor Torpedo boat, the MGB designation was dropped.
There are no known survivors, other than two abandoned wrecks, one in Chatham, England and the other in Ellingsøy, Norway.