Deliberate mistake: Because Stephen Greif tore an Achilles tendon playing squash, a stand-in had to complete his scene with Servalan in Ensor's underground complex. The result was a very odd segment in which we hear Travis' voice (pre-recorded by Greif) answering Servalan's lines, but never see him - except for an awkward shot of shuffling, black-booted feet that are all-too-obviously not Greif's.
Blake's 7 (1978)
1 deliberate mistake in Orac - chronological order
Starring: Jan Chappell, Michael Keating, Paul Darrow, Peter Tuddenham
Revealing mistake: The double-bladed axe one of the Decimas uses to attack the station windows is wobbling as he strikes with it. Small wonder he's not getting far at breaking in, with a weapon made of rubber. (00:22:30)
More trivia for Blake's 7