In addition to playing a German Officer in this movie (mostly speaking in English), Sir Christopher Lee dubbed the voice of the Dennis Price character in the scenes where he is speaking in German.
(At around forty minutes) Major Hitchcock (Terry-Thomas) goes to watch In Which We Serve (1942)," where he finds half the company. Sir Richard Attenborough plays one of the privates watching the film. Attenborough also happened to star in that movie.
William Hartnell made a career out of playing tough military NCOs in movies and on television. However, in real-life, he joined the Royal Armoured Corps in World War II, but was invalided out within eighteen months due to a nervous breakdown.
The closing epilogue and dedication states: "To all those who got away with it, this film is most respectfully dedicated."
In his 2013 novel "Expo 58", Jonathan Coe gives his hero two work colleagues named Windrush and Tracepurcel.