I need the name of a movie made in the 40's?

about a guy who get's hit on the head and has amnesia and get remember he was suppose to marry a particular girl who subsequently becomes his secratary and tries to remind him of who she is but he does not remember etc ... then of course he does and bla bla bla ... they live happily ever after kind of thing....I thought the girl was merle oberon but am not sure ...and I can not remember the guys name ... he is an English actor in the order of Sir Lawrence Olivier ... James Mason .. but a little earlier than James Mason .. that is all I can remember about it .... I remember there was a house in the movie with a white picket fence ... and he worked in a skyscraper type place in New York or London .. I can not remember if the film is British or American ... I seem to have a vague memory that the name may have the word "Double" in it but don't quote me on that ... I have "amnesia" about it ...ha ha ... just kidding