Bryan Forbes looked for that house with the turret as a film location; when he went to the owner for permission, she asked who was in the film. When told that an American actress named Kim Stanley, the woman blanched, stepped back, and said that Stanley was one of her oldest friends whom she had not seen in 17 years.
Richard Attenborough wears a prosthetic nose for his role in this movie.
During filming, Richard Attenborough developed kidney stones and was unable to work for an entire day. Since filming was on such a tight schedule, director Bryan Forbes got into costume played his role for some shots.