Like most Doctor Who serials from the 1960s, only filmed copies survive, the original videotape broadcast versions long ago having been erased. For the 2002 DVD release, as an experiment, a 3-minute segment of this episode went through the vidFIRE process, which restored the original videotape look to the film. It is included as an Easter Egg on the DVD; all subsequent 1960s episode releases (when possible) were released vidFIRE-restored.