The Doctor's quotation from T.H. Huxley, comparing life to a chess game, comes from Huxley's essay "A Liberal Education; and Where to Find It," originally delivered in 1868 at the South London Working Men's College. The Doctor's rendering is slightly off the original text, and it leaves out a linking sentence regarding the nature of the metaphorical chess game: "The player on the other side is hidden from us. We know that his play is always fair, just, and patient." While the Master's play is patient and, for the moment, hidden, it is neither fair nor just.
This episode was watched by 5.8 million viewers on its original transmission.
Anthony Ainley wanted to play The Master in the same low-key menacing manner as Roger Delgado did, but the producers insisted that his performance should be over-the-top. He would finally allowed to play The Master in Delgado's style in the episode Survival: Part Two (1989).