MINCEMEAT was a great British bluff, the first of really two that changed the course of the second world war.
Probably the supreme example was the second British bluff involving the Spanish double agent Juan Pujol, aka GARBO, and the fantastic exercise of absolutely convincing the German High Command that the invasion of Europe by the Allies would take place anywhere between Par De Calais and Norway, not Normandy. GARBO used 27 imaginary agents to support his reports to the German Abwehr of various non-existant allied forces building in Eastern England. He so convinced the Germans that months after the Normandy OVERLORD invasion they expected the main invasion to still come towards the North of Europe. GARBO received £20,000 from the Germans to finance his work, and the Iron Cross from Hitler. He also received the British Kings Medal For Service In The Cause For Freedom after the war.
GARBO is considered by many historians as being the key in the success of D-Day. A tremendous, unique, achievement and well worth reading about!
Recommended books for those interested:
Seaman, M. GARBO The Spy Who Saved D-DAY The National Achives (2004)
West, N. MI5 British Security Service Operations 1909-1945 Bodley Head (1981)