Before filming started, author H.G. Wells told everyone connected with the movie how much he'd hated Fritz Lang's film Metropolis and how he wanted them to do the opposite of what Lang (whom he called "Lange") and his crew had done.
Music recorded at The Scala Theatre, Charlotte Street, London, England UK
The date on the newspaper in the scene in 1966 when the war ends is 21st September 1966 - which would have been the 100th birthday of H.G. Wells.
The Image Entertainment DVD promises a 97 minute version "restored from the original 35mm masters." The version on the disc runs only 92 minutes, shorter than some VHS versions, but has better print quality than most previous releases.
The part of Theotocopulos was originally filmed with Ernest Thesiger in the role. The scenes were re-shot with Sir Cedric Hardwicke because the producers wanted a better-known actor with more "marquee value".