May 14, 1080 - Walcher, Bishop of Durham and Earl of Northumberland, was murdered. In revenge, William the Conqueror ravaged the area. He also used this as an opportunity to invade Scotland and build the castle at Newcastle-upon-Tyne.
May 14, 1264 - Simon de Montfort defeated Henry III at the Battle of Lewes. Montfort is known as the founder of parliamentary representative government (and thus not a favorite of the King!).