The entire serial was thought lost until 2013, when it was found in a storage room in a Nigerian television relay station. The storage room had been abandoned for decades, and several tapes of other BBC productions were in a bad condition. Fortunately, the tapes of this serial were not affected, which allowed a full restoration and a DVD release.
This episode takes place in 2018.
The helicopter explosion is footage from the James Bond film From Russia with Love (1963). The clip would be used again in The Dæmons: Episode Three (1971).
This was the first Doctor Who (1963) serial to be explicitly influenced by the James Bond action-adventure film franchise, which would have a greater impact during the Jon Pertwee era.
Director Barry Letts suggested the opening chase sequence featuring a helicopter and a hovercraft, replacing logistically-difficult scenes set at a crowded holiday resort.