Four to Doomsday

Four to Doomsday is the second serial of the 19th season of the British science fiction television series Doctor Who, which was first broadcast in four twice-weekly parts on BBC1 from 18 to 26 January 1982.

In the serial, Monarch plots to invade Earth for its minerals using a deadly toxin to wipe out humanity so he can continue to make improvements to his ship.

The TARDIS crew become separated and the Fifth Doctor and Tegan reach the bridge where the green-skinned commander introduces himself as Monarch, ruler of Urbanka, and his associates and fellow Urbankans are the Ministers of Enlightenment and Persuasion.

Shortly afterwards Enlightenment and Persuasion assume human forms, dressed in garments Tegan designed to demonstrate contemporary Earth fashions.

The TARDIS crew are reunited as guests, and it becomes apparent that there are four distinct human cultures represented on the vessel by a small group of humans – Ancient Greeks, the leader of whom is the philosopher Bigon; Chinese Mandarins and their leader Lin Futu; Princess Villagra and representatives of the Maya peoples; and Kurkutji and his tribesmen, of a very ancient Australian Aboriginal culture.

Monarch believes that if he can move the ship faster than the speed of light, he can pilot it back to the beginning of time and discover himself as God.

Enlightenment and Persuasion are decircuited, while Monarch himself (whom the Doctor realises is still organic as there is an oxygen-producing flora chamber on the ship) is exposed to the poison and shrunk.