Warn That Man (1943)
Warn That Man is a 1943 British thriller film directed by Lawrence Huntington and starring Gordon Harker, Raymond Lovell and Finlay Currie. It was based on a play by Vernon Sylvaine. During the Second World War, the niece of a peer is kidnapped and an impersonater takes her place as part of a German attempt to assassinate a politician.
More at Wikipedia.