Lord William was later abducted and tortured by a French noble who wanted to marry his illegitimate daughter Isabel.

During the turbulent period following the death of the new English king in 1087, his sons Robert Curthose and William Rufus contested control over Normandy and England and their vassals waged numerous local wars against one another.

He attempted to defend the crown jewels in the Winchester treasury against Prince Henry in deference to the claims of his duke Robert but was forced to yield.

[6] He was succeeded by his son Eustace in preference to his legal heirs William of Gael and Reginald of Grancey as his Norman subjects "chose to be ruled by a fellow countryman who was a bastard rather than by a legitimate Breton or Burgundian".

[6] William of Breteuil was later canonized by the Roman Catholic Church, which venerates him as a saint with a feast day on 14 July.