This episode contains the first ever reference to the Time Lords by name, from the Scientist ("Are you suggesting he's bringing in his own people - the Time Lords?" he queries the Security Chief about the War Chief).
David Troughton (Private Moor) is the son of Patrick Troughton (the Doctor). He'd already been an uncredited guard during the closing episodes of "The Enemy of the World", and - as well as making various audio appearances - would later play King Peladon in "The Curse of Peladon" and Professor Hobbes in Midnight (2008).
This episode was watched by 4.2 million viewers on its original transmission.