"Hamelinus comes Guarennie" confirmed donations to Saint-Victor-en-Caux made by "Guillelmus de Guarenna et comes Guillelmus filius eius", for the soul of "uxoris mee Ysabel", by undated charter, witnessed by "Guillelmum de Guarenna filium meum…". "Hamelin…comes de Waringe et ecclesie beati Bertini advocatus" donated land "in parochia de Rokesthorn" to Saint-Bertin, for "uxoris mee filiique mei Willelmi", by charter dated to . “Hamelinus comes de Warenna” donated property to Slevesholm Priory, with the consent of “Ysabellæ comitissæ uxoris meæ et Willielmi filii nostri”, by undated charter. An undated charter of ”Johannes comes Warennæ” confirmed earlier donations to Thetford Priory by “Hamelinus comes Warenniæ” with the consent of “Isabellæ comitissæ Warenniæ uxoris meæ et Willielmi de Warennia filii et hæredis mei”.
He succeeded his father in 1202 as Earl of Surrey. He received Grantham and Stamford, co Lincoln, 19 Apr 1205 as compensation for the loss of his lands in Normandy.
An undated charter of ”Johannes comes Warennæ” confirmed earlier donations to Thetford Priory by “Willielmus comes de Warennia” for the soul of “Matildis comitissæ uxoris meæ”. According to the Complete Peerage, “she [William's first wife] is alleged to have been daughter of an Earl of Arundel and to have died 6 Feb 1216.”
The Annals of Tewkesbury record the death in May 1240 of “Willelmus comes Warenniæ”. 1
William de Warenne, Knt., 6th* Earl of Surrey, of Lewes, Sussex, Reigate, Surrey, Conisbrough and Sandal (in Wakefield), Yorkshire, etc., a justiciar of England, custodian of Bamburgh and Knapp Castles, King's councillor, Warden of the Cinque Ports, 1216, Sheriff of Surrey, 1217-26, son and heir.
He witnessed a charter for King Richard I at Rouen in 1197. In 1202 he had seisin of his father's lands. In 1204 he was granted a yearly fair at Wakefield, Yorkshire. In 1205 the King granted him Grantham and Stamford, Lincolnshire to compensate him for the loss of his lands in Normandy. In 1206 he owed 100 marks for an advance made to him in Poitou, and 100 marks for robes provided for him there. In 1206 he was directed to escort William, King of Scots to York.
In 1213 he witnessed King John's submission to the Pope and resignation of the crown. He was security for the king in his promise of concessions to the Barons 10 May 1215. He took part with the Barons in the seizure of London 24 May 1215, and on 15 June at Runnymede was one of those who advised the king to grant the Great Charter (Magna Carta).
In 1227 he joined the Earl of Cornwall at Stamford in his revolt against the king, but at Christmas was with the king at York. In 1229 he was about to make a voyage on the king's service.
He was heir in 1234 to his sister, Isabel de Warenne, widow of Gilbert de l'Aigle.
In 1236 he acted as Butler at the coronation of Queen Eleanor of Provence, in place of his son-in-law, Hugh, Earl of Arundel.... 2
* a number of sources make William de Warenne 5th Earl of Surrey.