Mick Jagger owned an original four-rotor Enigma encoding machine which he loaned to the film for historical accuracy in constructing props.
When he's tapping on the desk with a pencil, Tom is spelling out "Claire" in Morse code.
When Hester Wallace decodes the long list of Polish names the camera zooms in on the name "Zygalski". Henryk Zygalski was a Polish mathematician who helped to break Enigma.
Hester Wallace adjusts her spectacles 16 separate times throughout the movie.
The Bletchley Park mansion in this film is not *the* actual Bletchley Park mansion, but another property. According to the tour guides at the real thing, the real Bletchley Park did not look enough like Bletchley Park to the production company to have been used in the film.
The scarf that Tom wears throughout the film is a King's College Cambridge scarf, which is the college Tom is a fellow of in the book.
Kate Winslet was pregnant with her daughter during the filming of this movie, so the schedule was arranged around that, and at the end of the movie when her character is pregnant, she didn't need a prosthetic.
Gastrolle: [Mick Jagger] Jagger--the film's producer--is sitting at a dinner table at the dance.
Thomas Jericho is loosely based on real-life mathematician and code-breaker Alan Turing (1912-1954).