The 655th episode of Doctor Who airs on BBC1. Lynda Bellingham, Michael Jayston and Honor Blackman guest star; Anthony Ainley appears as the Master. Though no one realizes it at the time of production, this is Colin Baker’s final appearance as the sixth Doctor before the BBC replaces him in the role. It’s also the final Time Lord story until well into the new series of the 21st century. The 23rd season of Doctor Who, and the trial storyline, concludes with this episode.