1986

History of the Doctor Who Universe
By this year International Space Command had regular Lunar flights and maintained a tracking station in Antarctica (DW: The Tenth Planet)

December
Humans first detect the Planet Mondas returning to the solar system, while it apparently was in orbit between Mars and Venus. The manned atmospheric probe Zeus IV is destroyed by the Cybermen inhabitants, and they go on to launch an attack on the Earth, starting with the Snowcap base in Antarctica. They plan to use a Z-bomb located here to destroy the Earth as one of their two worlds needed to be destroyed to save the other, but when they fail, Mondas is destroyed instead.

The doctor was present during this events and the strain it put on him trigered the regeneration from his first incarnation into his second. (DW: The Tenth Planet)

February

 * 22 - Donald Eccles (Krasis in The Time Monster) is killed in a road accident in Brighton, England, UK.

June

 * 11 - Reed De Rouen, who played Pa Clanton in "The Gunfighters," dies.

September

 * 06 - The Mysterious Planet Episode 1 First Broadcast (The Trial of a Time Lord Episode 1). The series returns to its original 25-minute episode format.


 * 13 - The Mysterious Planet Episode 2 First Broadcast (The Trial of a Time Lord Episode 2)


 * 20 - The Mysterious Planet Episode 3 First Broadcast (The Trial of a Time Lord Episode 3)


 * 27 - The Mysterious Planet Episode 4 First Broadcast (The Trial of a Time Lord Episode 4)

October

 * 04 - Mindwarp Episode 1 First Broadcast (The Trial of a Time Lord Episode 5)


 * 11 - Mindwarp Episode 2 First Broadcast (The Trial of a Time Lord Episode 6)


 * 18 - Mindwarp Episode 3 First Broadcast (The Trial of a Time Lord Episode 7)


 * 25 - Mindwarp Episode 4 First Broadcast (The Trial of a Time Lord Episode 8)


 * 28 - Ian Marter, who played companion Harry Sullivan, dies from a diabetes-related heart attack in London.

November

 * 01 - Terror of the Vervoids Episode 1 First Broadcast (The Trial of a Time Lord Episode 9)


 * 08 - Terror of the Vervoids Episode 2 First Broadcast (The Trial of a Time Lord Episode 10)


 * 15 - Terror of the Vervoids Episode 3 First Broadcast (The Trial of a Time Lord Episode 11)


 * 22 - Terror of the Vervoids Episode 4 First Broadcast (The Trial of a Time Lord Episode 12)


 * 29 - The Ultimate Foe Episode 1 First Broadcast (The Trial of a Time Lord Episode 13)

December

 * 06 - The Ultimate Foe Episode 2 First Broadcast (The Trial of a Time Lord Episode 14). Although not widely known at the time, this would be Colin Baker's final appearance in the series.

Unknown date

 * John Flint, who played William des Preaux in "The Crusade" and Captain Urquhart in "Time-Flight," dies.