Das ganz große Ding(1966)

After serving his prison sentence, Dickie Gray wants to leave his life as a petty criminal behind for good. However, he didn’t count on his old partner Marty: Marty has spotted a jeweler in London who looks exactly like Dickie and immediately starts planning the big heist. Dickie is initially reluctant, but eventually slips into the role of the jeweler after Marty kidnaps him.