Fulk FitzWarin at the time of his death in 1197. Whittington Castle lies on the English side of Offa's Dyke, which during the Norman era and before was the border between England and Wales. The site was fortified as a castle by William Peverel in 1138, in support of Empress Matilda, the daughter of King Henry I (1100–1135), in her struggle (known as The Anarchy) for the throne against King Stephen (1135–1154), grandson of William the Conqueror. In the late 1140s the lordship of Whittington, like Oswestry and Overton ceased to be part of England and became part of the Kingdom of
The Anarchy the spoils. William's son Henry I seized power after the death of his elder brother William Rufus and subsequently invaded and captured the Duchy of Normandy, controlled by his eldest brother Robert Curthose, defeating Robert's army at the Battle of Tinchebray. Henry intended for his lands to be inherited by his only legitimate son, seventeen-year-old William Adelin. In 1120, the political landscape changed dramatically when the "White Ship" sank en route from Barfleur in Normandy to England; around three hundred passengers died, including Adelin. With Adelin dead, the inheritance to the English throne was thrown into doubt. Rules of succession