Held primarily responsible, Truculent began to sink – 64 men were lost as she was ferrying workers as well as carrying her crew – and her wreck was towed to the destined nearby dockyard then sold for scrap.

Truculent spent much of her World War II wartime service in the Pacific Far East, save for early 1943, operating on the European shelf.

She took part in Operation Source, towing the X-class midget submarine X-6 to Norway to attack the heavy Kriegsmarine warships Tirpitz, Scharnhorst and Lützow.

[3] Fifty-seven of her crew were swept away in the current from a later-deemed premature escape – 15 survivors were picked up by a boat from the Divina and five by the Dutch ship Almdijk.

Most of the crew survived the collision and escaped, but died in the freezing cold mid-winter conditions on the mud islands that litter the estuary.

The story, of a British submarine on a training cruise that sinks after encountering a loose mine, is told from the perspective of the small group of survivors trapped under the sea.

The Producers have decided to offer the film in the spirit in which it was made, as a tribute to the officers and men of H.M. Submarines, and to the Royal Navy of which they form a part.