The Invasion of Time is the sixth and final serial of the 15th season of the British science fiction television series Doctor Who, which was first broadcast in six weekly parts on BBC1 from 4 February to 11 March 1978. It features the final appearance of Louise Jameson as the companion Leela. In the serial, the Vardans break the defences of Gallifrey to allow the Sontarans to invade and control the power of the Time Lords. Plot To the confusion of Leela and K9, the Fourth Doctor has a covert meeting with aliens before taking his companions to the Citadel at Gallifrey. Once there, he lays claim to the vacant Presidency as his right by Time Lord law—he is the only candidate, as established in the story The Deadly Assassin. While reviewing the presidential suite, he orders it lined with lead. During his induction ceremony, the Crown of Rassilon seems to reject him, and he's injured. Leela is accused of having attacked him, when in fact she tried to help him, and she's banished from the Citadel. Later, in front of the gathered Time Lords, the Doctor greets three figures that materialise within the Citadel, the Vardans, whom he had met before coming to Gallifrey, and addresses them as the Time Lords' new masters. Amid the confusion, the compliant Castellan Kelner kowtows to the Vardans and assists them in taking over, issuing arrests and ordering banishment for any Time Lords that he sees as disloyal. The Doctor confides in Chancellor Borusa, once they're in his lead-lined suite, that the Vardans can read their thoughts but lead blocks this. The Doctor plans to lock the Vardans in a time lock on their home planet as they are a dangerous race, but needed to keep up this facade in order to determine the location of their homeworld, and banished Leela for her own safety. The Doctor later explains the same to the Citadel guard commander Andred, using a force field from the TARDIS to shield his thoughts, to gain his help. Meanwhile, Leela has faith that the Doctor's actions are towards a larger goal, and along with the banished Time Lady Rodan, travel across the wastelands of Gallifrey. They meet a group of outsiders that have abandoned Time Lord ways, led by Nesbin. Leela explains the situation at the Citadel, and Nesbin agrees to help, assembling a resistance force to help take