On 8 May 1942, a French house painter named Rene Duchez arrived at the offices of an organisation in Normandy which was charged with building Hitler's Atlantic Wall, a colossal system of defences against Allied invasion. He found himself momentarily alone, and seeing a pile of maps on a desk he realised he was looking at a top-secret chart of the Normandy coastline. It showed everything from major fortifications to the positions of individual flamethrowers.
Duchez took the map and slipped it behind a mirror on the wall. Five days later, when he had finished decorating the offices, he retrieved the map and smuggled it out of the building in an old paint tin. The map was conveyed secretly to England on board a fishing vessel, and was to prove invaluable to the Allied chiefs of staff planning the D-Day invasions.