William FitzOsbern was probably raised at the court of his cousin William, Duke of Normandy, and like his father, became one of the ducal stewards.[3][b] He married Adeliza de Tosny, probably in about 1030. Together they founded Lyre Abbey (La Vieille-Lyre) and later Cormeilles Abbey.[1] FitzOsbern also founded Saint-Evroul Abbey.[4]
He was one of the earliest and most vigorous advocates of the invasion of England, and tradition holds that, at the Council of Lillebonne, he convinced the doubters amongst the Norman barons of the feasibility of the invasion. FitzOsbern's younger brother Osbern FitzOsbern was one of Edward the Confessor's chaplains, and possessed the rich church of Bosham in Sussex, where King Harold went to in the first scene of the Bayeux tapestry, and was well placed to pass along intelligence on the situation in England. He later became Bishop of Exeter.
In England after 1066
After William became King of England, FitzOsbern was made an earl, with major land holdings in Gloucestershire, Herefordshire, Oxfordshire, and the Isle of Wight, and smaller areas under his authority in Berkshire, Dorset, Wiltshire, and Worcestershire.[1] In the summer of 1067 King William returned to Normandy and left his half-brother Bishop Odo of Bayeux and FitzOsbern in charge of England during his absence.[1] The king was back in England in 1068 and FitzOsbern accompanied him in the subjugation of south-west England. He attended the King's Whitsun court in May 1068, and then visited Normandy, where he fell ill for some months.
In February or March 1069 FitzOsbern was asked by William to oversee the peace in York, where Gilbert de Ghent was made castellan of the new castle, but FitzOsbern returned south in time to attend the King's Easter court in April 1069 before returning to York.
Eadric the Wild launched a campaign of Anglo-Saxon resistance in the West Midlands, with the assistance of a number of Welsh princes (who had lately been allies of the Anglo-Saxon kings). In 1069 the revolt was crushed, and it is likely FitzOsbern played a major part in this, although the details are not certain. During this time FitzOsbern and his followers pushed on westwards into Wales, thus beginning the Norman conquest of the Welsh Kingdom of Gwent.
In 1070 trouble arose in Flanders, where King William's brother-in-law Count Baldwin VI of Flanders had died, leaving his county and his young sons in the hands of his widow Richilde, Countess of Mons and Hainaut. Her control of Flanders was challenged by the brother of her late husband, Robert the Frisian. Looking for help, she offered herself in marriage to FitzOsbern. He could not resist the chance to become also Count of this rich principality close to Normandy, and hurried there with his army. However, he was defeated by the Count of Flanders and killed in the Battle of Cassel on 22 February 1071.
William of Breteuil, who succeeded his father in Normandy. He was held captive and tortured by Ascelin Gouel de Perceval 'Lupus', Sire d'Yvry, until he finally granted his daughter Isabella de Breteuil in marriage to him.[5][6]
^Fitz Osbern's entry in the Oxford Dictionary of National Biography questions whether he was earl of Hereford: "He was not even 'earl of Hereford', as he appears in most historical writing. The king certainly made him an earl (comes) in England in 1067, but the title was personal, not territorial, and he had comital authority not just over Herefordshire but probably throughout the southern shires where Harold Godwineson had been earl."[1]
^In Normandy, he used the title comes palatii, count of the palace. Historian C. P. Lewis observed that "Historians writing in the nineteenth century and for much of the twentieth called William a 'palatine earl', an inappropriate translation of the title which he had used in Normandy; there were no palatine earldoms in England until the thirteenth century."[1]
Pierre Bauduin (2004). "Autour de la dos d'Adelize de Tosny : mariage et contrôle du territoire en Normandie (xie-xiie siècles)". Les pouvoirs locaux dans la France du centre et de l'ouest (VIIIe-XIe siècles) (in French): 157–173. doi:10.4000/BOOKS.PUR.27493. WikidataQ104804987.
F. Hockley (1980). "William Fitz Osbern and the endowment of his abbey of Lyre". Anglo-Norman Studies. 3: 96–105. ISSN0954-9927. WikidataQ104805001.
C. P. Lewis (1991). "The early earls of Norman England". Anglo-Norman Studies. 13: 207–223. ISSN0954-9927. WikidataQ104805132.