A Lancaster bomber dropping 'Window', the tin foil strips that appeared as a mass of aircraft on German radar.

Flying in box formation over an area 12 miles wide and eight miles deep, the aircraft had to fly in a continuous orbit gradually nearing the French coast, to give the impression of a large convoy heading slowly towards it. The effect was heightened by the Navy ships towing balloons which would reproduce a “big ship” type of echo on the enemy radar screens, and also by our aircraft jamming the German radar to prevent recognition of the “Window” deception.