25 November 1120 (900 years ago): The White Ship Disaster. This is probably the most catastrophic event of its kind in Europe. King Henry I of England loses his son and only heir, along with scores of important courtiers and other officials, when the White Ship sinks off the Normandy coast. There was only one survivor of about 300 passengers.
As a result, England is plunged into a period known as the Anarchy.