Claim: The four knights fled to Knaresborough Castle, founded by Norman Baron in c. 1100 on a cliff above the River Nidd, where they lived for a year after killing Becket on December 29, 1170.
Evidence: The castle was first built by a Norman baron in c. 1100 on a cliff above the River Nidd. Hugh de Morville and three other of King Henry II's knights, Reginald Fitzurse, William de Tracy, and Richard le Breton (or de Brito), plotted Thomas Becket's murder after interpreting the king's angry words (supposedly "What miserable drones and traitors have I nourished and brought up in my household, who let their lord be treated with such shameful contempt by a low-born cleric?") After Henry advised them to flee to Scotland, they subsequently took refuge in de Morville's Knaresborough Castle. They assassinated the archbishop in Canterbury Cathedral on 29 December 1170. In the 1170s Hugh de Moreville and his followers took refuge there after assassinating Thomas Becket. Thomas Becket (/ˈbɛkɪt/), also known as Saint Thomas of Canterbury, Thomas of London and later Thomas à Becket (21 December 1119 or 1120 – 29 December 1170), was Archbishop of Canterbury from 1162 until his murder in 1170. Tracy paid scutage on his lands in 1171 and set out for Rome after the end of September but before Henry II's expedition to Ireland in October.