The character Eric Stafford (Paul Brennen), a Special Operations Executive (SOE) combat instructor, has much in common with real life SOE combat instructor William Ewart Fairbairn. Stafford is said to have served with the Shanghai Municipal Police as did Fairbairn from 1907 until 1940.
The Naval Intelligence unit in Derby House, Liverpool that Foyle has applied to join has been recreated as the Western Approaches Museum.
Uncle Aubrey mentions that Sam used to read Edgar Wallace novels. Wallace was an incredibly prolific writer of crime, mystery, science fiction, and adventure books. He is best remembered for creation of "Sanders of the River" and the original draft of "King Kong." He died during the writing process of the latter film.
SOE trainee Mark Nicholson (Raymond Coulthard), a crime writer and amateur magician, tells Foyle that magic will be used during the war both to conceal an army and to create an illusion of troops that don't exist. In fact, British stage magician Jasper Maskelyne claimed to have commanded a squad in North Africa during World War II assigned to do just what Nicholson described.
Milner uses the phrase, "The lady vanishes." This is a reference to the Hitchcock spy film, The Lady Vanishes (1938), which came out two years before the setting of this story.