The master videotape of this episode was wiped by the BBC and no copy of it was known to exist until an almost complete film reel, held by a private collector in Hampshire, was discovered in July 2011.
This episode was watched by 11.3 million viewers on its original transmission.
When the return of this episode was announced one of the newscasters stated that the Chumblies was a precursor to the Daleks, despite the Daleks having been around for two years by the time this episode was made.