Trivia / X the Unknown

• Divorced Installment: The film was originally intended by Hammer to be a sequel to The Quatermass Xperiment, but Nigel Kneale refused permission for the character of Bernard Quatermass to be used.
• Hostility on the Set: Dean Jagger and other crew members, not to mention Hammer brass, all found Norman very difficult to work with, so much so that despite the film receiving some good notices, Hammer never worked with Norman again.
• Money, Dear Boy: According to Jimmy Sangster, director Leslie Norman was not overly interested in making this film, but did anyway for the sake of work.
• Uncredited Role: Anthony Sagar as a gateman.

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