X the Unknown

X the Unknown is a 1956 British science fiction horror film directed by Leslie Norman and starring Dean Jagger, Leo McKern and Edward Chapman. It was made by the Hammer Film Productions company and written by Jimmy Sangster, at the suggestion of Anthony Hinds. This was the first film Jimmy Sangster ever scripted, and its success started his entire screenwriting career. The film is significant in that "it firmly established Hammer's transition from B-movie thrillers to out-and-out horror/science fiction" and, with The Quatermass Xperiment (1955) and Quatermass 2 (1957), completes "an important trilogy containing relevant allegorical threads revealing Cold War anxieties and a diminishing national identity resulting from Britain's decrease in status as a world power".

The film's special effects were handled by Les Bowie and Jack Curtis, Bernard Robinson and Jimmy Sangster were Production Designers, Chris Sutton was Assistant Director and Phil Leakey did Makeup. As with Quatermass, Hammer played up the film's X Certificate in their advertising. Filming began the first week of January 1956, and premiered at the Pavillion on Sept. 21, 1956. In the UK, the film was released on a double bill with H.G. Clouzot's Diabolique.