He is more often referred to as Earl Warenne or Earl of Warenne than as Earl of Surrey.
Sometime around 1093 he tried to marry Matilda (or Edith), daughter of king Malcolm III of Scotland. She instead married Henry I of England, and this may be the cause of William's great dislike of Henry I, which was to be his apparent motivator in the following years.
He accompanied Robert Curthose (Duke Robert) in his 1101 invasion of England, and afterwards lost his English lands and titles and was exiled to Normandy. There he complained to Curthose that he expended great effort on the duke's behalf and had in return lost most of his possessions. Curthose's return to England in 1103 was apparently made to convince his brother to restore William's earldom. This was successful, though Curthose had to give up all he had received after the 1101 invasion, and subsequently William was loyal to Henry.
To further insure William's loyalty Henry considered marrying him to one of his many illegitimate daughters. He was however dissuaded by Archbishop Anselm of Canterbury, for any of the daughters would have been within the prohibited degrees of consanguinity. The precise nature of the consanguinous relationship Anselm had in mind has been much debated, but it is most likely he was referring to common descent from the father of duchess Gunnor.
William was one of the commanders on Henry's side (against Robert Curthose) at the Battle of Tinchebray in 1106. Afterwards, with his loyalty thus proven, he became more prominent in Henry's court.
In 1110, Curthose's son William Clito escaped along with Helias of Saint-Saens, and afterwards Warenne received the forfeited Saint-Saens lands, which were very near his own in upper Normandy. By this maneuver king Henry further assured his loyalty, for the successful return of Clito would mean at the very least Warenne's loss of this new territory.
William's death is recorded as 11-May-1138 in the register of Lewes priory and he was buried with his father at the chapter-house there.
- C. Warren Hollister, "The Taming of a Turbulent Earl: Henry I and William of Warenne", Historical Reflections 3 (1976) 83-91
- C. Warren Hollister, Henry I (2001)
- Warenne Family Ancestry
- John Badger Family Ancestry
- The Ecclesiastical History of Orderic Vitalis, ed. M. Chibnall, vol. 2, p. 264 (Oxford, 1990).