I loved you, I've never loved anyone else, I never shall

WATERLOO BRIDGE

1940

Directed by Mervyn LeRoy

Written by S.N. Behrman, Hans Rameau, and George Froeschel (based on the play by Robert E. Sherwood)

Spoiler alert: moderate (and severe, I suppose, for the 1931 film of the same name, which I recommend you never watch for fun)