As part of the plan to liberate Europe, it was crucial the Germans did not know the true target of the invading army. As the point on the English coast closest to France, Dover was an obvious place from which to launch an invasion force - and Calais was the obvious destination.
Even as the fleet set sail for Normandy, the Allies kept up a pretence that they were heading for Calais, with the RAF tricking the Germans into believing an attack was taking place. Nashreen Issa has been looking back at Operation Fortitude, the plan to deceive Hitler.
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Captain Mike Green, a senior flying instructor, was piloting the two seater helicopter involved in the crash.
Saturday evening's weather for the east
Saturday evening's weather for the west