Before filming started, author H.G. Wells told everyone connected with the film how much he'd hated Fritz Lang's film Metropolis (1927) and how he wanted them to do the opposite of what Lang (whom he called "Lange") and his crew had done.
The date on the newspaper in the scene in which the war ends is September 21, 1966, which would have been the 100th birthday of H.G. Wells.
Ralph Richardson stated that he intentionally modelled his character, the despotic boss of Everytown, after Italian fascist dictator Benito Mussolini.
At the time of its 1947 U.S. re-release, the film was most frequently shown on the top half of a double bill, with The Man Who Could Work Miracles (1936), which likewise was based on a novel by H.G. Wells and starred Ralph Richardson on the lower half of the program.
Several movie critics in the U.S. criticized H.G. Wells's screen adaptation of his book for its failure to adequately address class struggle. The complaint rang with a tone of irony for Wells, whose book had been criticized by literary critics for containing too much of the author's analysis of class struggle and his socialist-leaning political beliefs.