In the original script, the Vardans were to betray the Doctor, ordering his annihilation at the close of the episode.
Logan's Run (1976) was cited as one of the influences behind the story, in particular Leela and Rodan escaping from the Citadel into the wastes of Outer Gallifrey.
The first and only acting role of Gai Waterhouse.
This episode was watched by 9.5 million viewers on its original transmission.