The two 25ft Fast Motor Boats on display at Marchwood are of the standard Admiralty design which evolved from numerous types built by the well known boat builders pre-war. The Fast Motor Boat, used as a Captain's Boat, was first introduced to the Admiralty by British Power Boats early in 1935, when the first of this type, actually three of 24V2ft, were built for the HMS Enchantress, HMS Exmouth and C-in-C Fleet Portsmouth. Subsequently a series of craft, also by BPB Co, but of 25ft, were built for the "G" class destroyers.
Thereafter, Vosper, Thornycroft and Whites built numbers of 25ft FMBs all to their own designs. At the outbreak of WWII, these designs were built by other builders such as Brooke Marine, Aldous and others and like their predecessors all utilised petrol engines either of the Power Meadows or Vosper V8 types. Some of the earlier variants were carvel built, however by 1940 the standard Admiralty clinker hulled 25 ft FMB had evolved and was being built in great numbers by numerous builders. Boats from 1941 onwards were built with single Perkins P6M diesels; this type subsequently became the standard for most Admiralty FMBs. Dimensions, as listed in Admiralty documents, varied, - however those quoted are for FMB 441341.