There were, in fact, actually four 8mm reels released (which could be purchased in color or black & white, sound or silent), serializing the feature. This digest, when the reels were combined, runs about 36-40 minutes, depending on whether you were using the silent or sound versions. A well-edited condensation of the feature film. (The four reels were 1. "The Cyclops," 2. "The Strange Voyage," 3. "The Evil Magician" and 4. "The Dragon's Lair.")
To receive the original 'A' certificate in 1958 and then a 'U' certificate in 1962 the original UK cinema release was heavily cut by the BBFC who completely removed the skeleton fight, as well as making edits to the man roasting on a spit, the dancing snake woman, close-up shots of the Cyclops, and scenes of minor violence including fighting and shots of dead bodies. All later video releases were restored and uncut.