The 1st Doctor, Vicki and Steven stop the Meddling Monk's plan to destroy a Viking fleet and thus change history. King Harold II defeats the Viking invaders at Stamford Bridge in the north of England. King Harold II is defeated and killed by William the Conqueror at the Battle of Hastings. A monastery is built on the site of what will become Forgill castle in Scotland. Terror of the Zygons.
Exact date is conjecture.
Broton, disguised as the Duke of Forgill, says the monastery was built in the 11th century. Around this time, the Convent of the Little Sisters of St. Gudula is founded. The Stones of Blood. Exact date is conjecture. The convent is said to have been founded in the 12th century.