The production used hundreds of volunteer actors and a few professional filmmakers such as Sebastian Shaw and Reginald Marsh. Some extras were members of British science fiction fan clubs. Some British fascists in the film were actual ex-members of the British Union of Fascists. Some SS and Wehrmacht soldiers portrayed in the film were actual German army ex-servicemen.
Kevin Brownlow and Andrew Mollo began work on the film as teenagers and finished the film's mostly amateur production 8 years later. The Guinness Book of World Records credits this film to have the longest ever production schedule. Director Kevin Brownlow later became a film historian and Andrew Mollo became a military historian.
The film was shot in black and white on 16 mm film. Despite its grainy, newsreel feel, no actual stock footage was used. The filming equipment was mostly borrowed. The audio quality and lighting during the opening are poor, making the opening dialog difficult to follow. Stanley Kubrick donated film stock from 'Dr. Strangelove' to help finish this film. Wartime BBC radio announcers Alvar Liddell and John Snagge donated their services to reconstruct voice newsreels and radio broadcasts. Director Tony Richardson co-financed the final production.
Started in 1956, completed in 1964, not released until 1965.