At this point William was joined by his , Duke Godfrey of Brabant. Together their armies besieged Aalst on 12 July. But during the course of the siege William was wounded in the arm in a scuffle with a foot soldier. The wound became and William died at the age of twenty-five on 28 July 1128. His faithful , Helias of Saint Saens, was there with him. William’s body was carried to the abbey of St Bertin in St Omer and buried there. He left no children and was survived by his father, a prisoner of Henry I, who died six years later.