John Woodnutt had previously played Hibbert in "Spearhead from Space" (1970) and would later play the dual roles of Broton and the Duke of Forgill in "Terror of the Zygons" (1975) as well as Seron in "The Keeper of Traken" (1981). Luan Peters had previously appeared in "The Macra Terror" (1967) under her stage name Karol Keyes. Caroline Hunt previously appeared in "The Reign of Terror" (1964). Louis Mahoney later appeared as Ponti in "Planet of Evil" (1975) and as Billy Shipton in "Blink" (2007).