On the Double (film)

On The Double is a 1961 film, directed by Melville Shavelson, who also wrote the screenplay with Jack Rose. It stars Danny Kaye who plays, as in many of his films, two roles in this case, an American soldier and a British General.

Ernie is unable to fool the Generals wife, Lady Margaret Dana Wynter, but he is able to deceive the officers at a regimental party. On her advice, and to further the conceit, he appears to get drunk and has a fight with his wife. His harddrinking Scottish aunt, Lady Vivian Margaret Rutherford is highly suspicious, but is too drunk to take it further.The General also has a mistress, Sergeant Stanhope played by blonde bombshell Diana Dors, but Ernie finds out too late that she is a plant a German agent. With her connivance, he is kidnapped and taken to Berlin. There, he manages to confuse the German interrogators, who want information about the projected Normandy landings, by talking arrant nonsense about nonexistent operations and places. In the resultant confusion, he manages to escape and is chased through the streets of Berlin at night. ........

Source: Wikipedia