It was one of the most daring commando raids of World War II. Five two-man canoes, launched from a submarine in the Bay of Biscay, set out to paddle 70 miles upriver to attack shipping in Bordeaux harbour.
After the war the raid became the subject of a film, the Cockleshell Heroes, and was one the earliest operations by what became the Royal Marines' Special Boat Section.
But in a new book, A Brilliant Little Operation, Paddy Ashdown, himself a former SBS officer, reveals a story of Whitehall rivalry which almost certainly led to the needless deaths of many of those who took part.
The BBC's Nick Higham reports.
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