Negatives (1968 film)

Negatives is a 1968 British drama film directed by Peter Medak. Based on a novel by Peter Everett, it features Peter McEnery and Glenda Jackson as Theo and Vivien, a couple who act out their erotic fantasies by dressing up as the Edwardian murderer Hawley Harvey Crippen and his lover Ethel le Neve. Diane Cilento plays Reingard, a German photographer who becomes involved in their private world.

Source: Wikipedia