Triple Cross (1966) on Netflix

Safecracker Eddie Chapman's priorities in life are himself and carousing with beautiful women. In the first year of his possible fifteen year incarceration at a Jersey prison for a series of safecracking crimes committed in London, the Nazis take control of the island. With his special skill set, Eddie tries to negotiate working for the Nazis - for a fee and for his obvious release - against the British. Although the Nazis do not fully trust him, especially Lieutenant Keller, they do come to an agreement. He specifically signs an exclusive contract with Baron Von Grunen, who will be his handler. The contract is so the Baron can retain control over Eddie. Eddie is given the code name Franz Grauman, and all electronic correspondence he is to end with "XXX" as a sign that he is all right. That code becomes ironic as Eddie does enter into a triple cross as on first opportunity to makes a deal with the British to provide them with German intelligence in return for a full pardon on his prison sentence. This triple cross becomes an issue for all sides as Eddie tries to maneuver his way through what could be potentially enemy territory in France and Germany if the Germans ever found out his allegiance to the British. His possible downfalls include trying to remember what he should and should not know as he talks to both sides, and his weakness for the opposite sex, most specifically a Frenchwoman named Paulette who he met at a transit camp in France and who has ties to the French resistance, and the Countess Helga Lindstrom, a Swede working for the Nazis.