1066

1066 was the year in which the Battle of Hastings was fought in England, resulting in the death of Harold Godwinson and the Normans taking control of England under William the Conqueror.

The Monk tried to change the outcome of this battle so the Saxons wouldn't be defeated by the Normans. He tried to thwart a Viking invasion in the north, thus keeping Harold Godwinson and the English army from having to fight Harald Hardrada and the Vikings at Stamford Bridge, and therefore would be better prepared for the Battle of Hastings. He was stopped when Saxons from Wulnoth's village attacked his monastery, driving him out, and the Doctor removed the dimensional control of his TARDIS, stranding the Monk there. (TV: The Time Meddler)

On the field of battle, the Eighth Doctor and Mary Shelley met King Harold (AUDIO: Mary's Story) while the TARDIS' helmic regulator was hit and incapacitated by an arrow when the Eleventh Doctor visited the battle. (WC: Pond Life: Part 5)

At the conclusion of the battle, according to one account, Harold's body was intentionally misidentified by Countess Gytha and Lady Edith Swan-Neck. In fact, Harold had survived the battle, but the false identification allowed him to die as Harold but be "reborn" as Hereward the Wake. (PROSE: The Real Hereward)

Halley's Comet passed Earth in April (PROSE: The Time Meddler) of this year, where it crashed into a Persopolisian ship, the wreckage of which fell to Earth. (AUDIO: The Time Capsule)

William was crowned King of England on 25 December of this year, and the Monk witnessed this occurrence. (PROSE: The Time Meddler)

Building of the Tower of London began. (PROSE: Magic of the Angels)

Behind the scenes
According to the "Earth-Skaro Timescale" of Terry Nation's Dalek Annual 1976, the Earth year 1066 is concurrent to Skaro-year 9143, when the Daleks invaded Venus and Mars.