a Primord was inspired by Shakespeare's play Richard III (because of the Primord creature's hump). Caroline John said she enjoyed her role as Section Leader Elizabeth Shaw, as it was fun playing Liz as a "baddie". She also said she hated doing the scenes in which she was playing her usual role, because it was boring compared to playing the parallel character. She was upset, though, about the scene in which Section-Leader Shaw shot Brigade Leader Lethbridge-Stewart, as she was pregnant at the time. As a result, the scene was recorded with the weapon fired from out-of-shot, after which Shaw was shown returning the gun to her holster. Her pregnancy made it impossible for her to continue in the show, and this became her final serial. During the scenes set on the parallel Earth, images of the British Republic's leader are seen on posters. The image used is that of BBC visual effects designer Jack Kine, in homage to the 1954 BBC adaptation of Orwell's novel Nineteen Eighty-Four in which the face of Big Brother was actually that of the BBC's head of television design Roy Oxley (Kine had worked on the visual effects for that production). Episode 6 has a small damaged section on the American NTSC videotape which was used as the source of the colour signal for the restoration, which the Doctor Who Restoration Team replaced by recolouring the appropriate section of the b/w film recording. Locations The exterior shots used in this production were filmed at Kingsnorth Industrial Estate in Medway, Kent which featured as the setting for the Inferno project. Music Director Douglas Camfield chose not to commission any new incidental music for the serial, but instead made use of existing library recordings by members of the BBC Radiophonic Workshop. These included: "Blue Veils & Golden Sands" and "The Delian Mode" (both by Delia Derbyshire); "Battle Theme", "Homeric Theme", "Attack of the Alien Minds" and "Souls in Space" (all by Brian Hodgson); and "Build Up To" (by David Vorhaus). In addition, as was usual, Brian Hodgson supplied new sound effects for the serial, including "Tardis Control On & Warp Transfer". According to the DVD release notes from the ITV serial Timeslip, this music subsequently featured in the second episode of that show's serial The Time Of The Ice Box. Cast notes Christopher Benjamin, who plays Sir Keith Gold, subsequently appeared as Henry Gordon Jago in