 This is the second episode to show a Time Lord other than the Doctor regenerating on screen (and the first of the revived series), the first being the regeneration of K'anpo in "Planet of the Spiders" (1974); although Romana regenerated in the first episode of "Destiny of the Daleks" (1979), this process was depicted off screen.The Master continually hears the sound of drums throughout this episode; this continues through "The Sound of Drums", "Last of the Time Lords" and becomes a plot point in "The End of Time".This episode was announced as the first of a three-part story in "Totally Doctor Who", broadcast the day before.