In the pub, early on just after P/O Rawlings has joined, Flt. Lt. Murray tells him their boats can do 30 knots. Watch closely - his lips show he says 40 knots. This dub was probably made at the request of military censors since the film was released during WWII. Their boat is HSL 183 which was a Type 2 63 ft. HSL high speed launch craft made by the British Powerboat Company between 1940 and 1942. The boats could achieve over 36 knots, and the later Type 3 had a maximum speed of over 40 knots.
James Robertson Justice's debut.
Opening credits prologue: The characters portrayed are fictitious, but the events are based on facts.