The real-life equivalent of the James Robertson Justice character was actually in Army Intelligence, not Naval Intelligence, as in this movie. The change was made because Justice refused to shave off his trademark beard, and Army officers were not allowed them.
This movie is based on World War II's 1942 Operation Salaam. The German movie Rommel ruft Kairo (1959) and the American mini-series The Key to Rebecca (1985), and its source novel by Ken Follett are also loosely based on Operation Salaam.
This book's source film tie-in novel by Leonard Mosley has the longer title of "Foxhole in Cairo: a True Spy Story From the Nazi Third Reich".
This movie was based on a true story, a title card states that this movie was "a true story of the war".
Publicity for this movie boasted that it was "The Greatest Spy Story of the Desert War!"