Mantes : the last battle

William's final years were marked by further trials. In England, the betrayals of the Norman barons followed revolts by the Anglo-Saxons. In 1075 it was Roger de Breteuil, Count of Hereford, and son of his most loyal friend William FitzOsbern, killed in his service at Cassel in 1071. In 1082 there was a much more serious matter which led William to arrest his half-brother, Odo de Conteville, Bishop of Bayeux and Count of Kent. He had imposed numerous tax demands on the population of his English county and ultimately raised a private army whose purpose was unclear. William had him tried and imprisoned.

The dispute with his son Robert Curthose, who claimed his share of William's estates, had not been resolved when in 1083 his wife Matilda, the Duchess-Queen, died. At the end of his father's reign, Robert continued to pursue intrigues against him at the court of the King of France, Philip I. William's problems at the frontiers had, moreover, not abated. Although a threatened Danish invasion did not materialise between the end of 1084 and 1086, it did oblige William to return to England. Upon his return he had to put an end to the interminable siege of Sainte-Suzanne through negotiation (1086) and then turned against the King of France.

Control of the Vexin region set the King of France and the Duke-King in opposition. This region is an open space between central Normandy and the royal domain around Paris. The frontier artificially separates a Norman Vexin and a French Vexin. Each tried to push it towards the other's domains. The King of France had reinforced his controls over the lay and ecclesiastical lordships in the French Vexin, and through them launched attacks on the Norman Vexin. William decided to launch a reprisal raid. The sortie took place at Mantes in July 1087. William was accidentally wounded. He died a few days later in Rouen (9 September 1087) and his body was transported for burial to the abbey of Saint-Stephen in Caen.

On his death bed William divided up the domain he had been at such pains to keep under his control: for Robert, the rebellious older son, Normandy, for William Rufus, the younger, England, Henry the youngest, was excluded.