Operation Mercury

Thus was a British deception plan, otherwise known as the 'Southern Railway Plan', to use the double agent 'Tate' to pass to the Germans false plans for the movement of Allied troops for embarkation in south-eastern English ports and thereby persuade the Germans that the Allied main invasion effort was not the already-committed 'Overlord' but a larger landing in the Pas de Calais region (8/14 June 1944).