Robert was made Earl of Northumbria after Aubrey de Coucy, the previous earl, decided that he no longer wished to remain in his post. Coucy was made earl in 1080 and, probably that same year, resigned his position and returned to Normandy, losing all of the lands that he held in England. He was not replaced until Robert was appointed in 1086. In 1088, Robert and his uncle, Geoffrey, sided with Robert, duke of Normandy, in the rebellion against William Rufus, and both were active militarily. The rebellion failed but the king subsequently pardoned them both, and Robert remained in his post as Earl of Northumbria. In November 1093, Malcolm III of Scotland invaded Northumbria for the second time since 1091, and attacked Alnwick. Robert de Mowbray raised an army and attacked the Scots taking them by surprise on 13 November. In the ensuing Battle of Alnwick, Malcolm and his son Edward were slain. Earlier that same year, Geoffrey de Montbray died and Mowbray succeeded to his uncle's large estates, so becoming one of the most powerful barons in the kingdom. In 1095, Mowbray married Matilda, daughter of Richer de l'Aigle, and niece of Hugh d'Avranches, 1st Earl of Chester.
Rebellion and downfall
In 1095 Mowbray took part in a rebellion which had for its object the transference of the crown from the sons of the Conqueror to Stephen of Aumale. It appears that there was a conspiracy that included several barons, but that when the time came for action most of the conspirators abandoned the scheme leaving Mowbray and his fellow conspirator William of Eu exposed. The incident that brought the matter to a head was Mowbray seizing four Norwegian vessels lying in the Tyne. The merchants who owned the vessels complained to the king and Mowbray was commanded to attend the Curia Regis to explain his actions. Mowbray did not attend and ignored further summonses, so that William finally led an army against him. Mowbray shut himself up in his stronghold, Bamburgh Castle. William laid siege to Bamburgh and built a temporary siege castle alongside it, known as Malvoisin, or "evil neighbour". For some reason, during the siege, Mowbray left the castle with a small force of knights and was pursued by his besiegers, being forced to take refuge in Tynemouth. After a siege ofsix days he was wounded in the leg, captured and was taken back to Bamburgh where his wife was still resisting the besiegers. She finally surrendered the castle after the besiegers threatened to blind her husband.
Imprisonment and death
As a result of his part in the rebellion Mowbray forfeited his estates and was imprisoned for life, initially at Windsor Castle. He spent many years in prisons, "growing old without offspring", according to the chronicler, Florence of Worcester, and then was allowed to become a monk at St Albans Abbey, according to another chronicler Orderic Vitalis. There is some doubt about the date of his death. On one hand it was claimed that he spent thirty years in prison, giving his date of death about 1125. However, William Dugdale claimed that Mowbray became a monk and died in 1106. Mowbray’s fellow conspirators, William of Eu and William of Aldrie, received harsher punishment, William of Eu being castrated and blinded, and William of Aldrie being condemned to death.
Legacy
gives the following description of Robert de Mowbray: "Powerful, rich, bold, fierce in war, haughty, he despised his equals and, swollen with vanity, disdained to obey his superiors. He was of great stature, strong, swarthy and hairy. Daring and crafty, stern and grim, he was given more to meditation than speech, and in conversation scarce ever smiled". Mowbray's wife, Matilda, was granted an annulment of her marriage by Pope Paschal II and sometime after 1107, she became the wife of Robert's brother Nigel d'Aubigny, who was also granted the lands in Montbray forfeited by her former husband. The couple remained childless and in 1118 d’Aubigny divorced Matilda and married Gundred de Gournay, daughter of Gerard de Gournay and Edith de Warenne. They had a son, Roger, who inherited the estates originally forfeited by Robert Mowbray. On receiving his inheritance Roger changed his name to Mowbray at the instruction of Henry I. Thus the name Mowbray was continued, but with no blood line from Robert de Mowbray.
