A memorial to the Royal Marines who canoed almost 100 miles behind enemy lines to blow up ships in a daring World War II raid has been unveiled in France. But what did the secret mission entail, and why was it so important?

For 10 marines in December 1942, their secret mission was so daring and dramatic they were hailed as the Cockleshell Heroes and in 1955, immortalised in film.

Unbeknown to them when they signed up for "hazardous service", their job was to the attack enemy German ships moored at the port of Bordeaux in occupied France from their canoes.

Only two men survived to tell the tale, but its significance reportedly led Winston Churchill to say he believed the raid could have shortened the war by six months....