The Divorce of Lady X

The Divorce of Lady X is a 1938 British colour romantic comedy film made by London Films it stars Merle Oberon, Laurence Olivier, Ralph Richardson and Binnie Barnes. It was directed by Tim Whelan and produced by Alexander Korda from a screenplay by Ian Dalrymple and Arthur Wimperis, adapted by Lajos Br from the play Counsels Opinion by Gilbert Wakefield. The music score was by Mikls Rzsa and Lionel Salter and the cinematography by Harry Stradling.

Leslie Steele Merle Oberon, a guest at a costume party, is forced to stay overnight in a hotel because of a particularly bad London fog. As there are no rooms available, Steele talks her way into sharing a suite with Everard Logan Laurence Olivier, a handsome but somewhat stiff lawyer. They spend the night together, quite chastely, but Logan becomes convinced that Leslie must be married. His conviction is confirmed when an old school friend, Lord Mere Ralph Richardson, arrives and asks Everard to represent him in a divorce case against his wife, Lady Claire Binnie Barnes.

Source: Wikipedia