The colour videotape of this first episode was wiped by the BBC but a 16mm black & white engineering print of the episode was returned to the archives in 1983. This is chronologically the last episode of Doctor Who (1963) to be affected by the BBC's archive purges of the 1970s, as all subsequent episodes of the series exist on their original PAL master tapes.
Producer Barry Letts often stated that he was very disappointed with the quality of the model dinosaurs built for this serial. They were created not by the BBC Visual Effects Department but by a freelance effects designer. In a 2004 interview, he named this serial as the one he would most like to do again but with modern technology. He said: "Just imagine what it would have looked like if we had had the resources of Walking with Dinosaurs (1999)!"
Private Ogden was to feature in later parts of the stories but George Bryson was not free during that chunk of taping, so Ogden's lines were given to a character named Bryson.
Whilst Episode 1 exists in the BBC archives as a black-and-white copy, it was colourised for the DVD release which uniquely features the option to watch either the black-and-white version or the colourised versions.
There is a longstanding fan myth that the master tape of this episode was wiped by mistake and had been confused with an episode of the Patrick Troughton serial "The Invasion". In fact, the BBC issued specific instructions to wipe all six episodes of this serial just six months after the story's transmission; for reasons unknown, only this episode's master tape was wiped.