Writer Derek Marlowe once said of Laurence Harvey's partial direction of this movie: "He directed his own mis-talent, changed it and the script, which is rather like Mona Lisa touching up her portrait while Leonardo is out of the room."
When Eberlin visits Caroline's apartment, she picks up her camera to take a picture of him. As she picks it up, a quick closeup of the table it's sitting on shows another object on the table: a Frank Sinatra album, "Strangers in the Night." Mia Farrow was married to Sinatra at the time.
The ending was directed by Laurence Harvey, who also directed some scenes shot in West Berlin, Germany. Producer and Director Anthony Mann directed all of the scenes in Surrey and London, as well as some of the West Berlin scenes.
Cinematographer John Alton, who had retired in 1960, met former colleague Anthony Mann in a Swiss casino high up in the Alps. Mann was directing this movie at the time and wanted Alton to shoot his next movie. Alton agreed to talk to him about it the next day, but Mann died before their meeting. According to Alton, "He'd been losing so much money at the casino, that probably helped kill him. The industry lost a great man." Laurence Harvey completed the movie.