 The MTB used in this film is actually MTB 102 an extremely important  and illustrious boat used throughout WWII including during the  Dunkirk evacuation of British and French forces in 1940 where it  actually became the flagship of the fleet when the Admiral in charge  of the operation transferred his flag to the boat after his  destroyer was sunk. The production company paid for the completion  of its restoration after being used by a local Sea Scout troop on  the Norfolk Broads. The boat is still afloat and has a vast number  of related articles about it on the internet including those about  its design heritage and timely build just prior to the beginning of  the war. A true historic boat.