William of Douglas accompanied his uncle, who had been appointed Guardian of the Realm, to the battlefield of Halidon Hill. There, with his uncle, six belted earls and countless knights and commoners, he was slain. He died unmarried and a minor. The title and privileges of the Lordship of Douglas passed to another uncle, Hugh "the Dull", a Canon of Glasgow and parson of Roxburgh who turned much of the Douglas patrimony over to his cousin William Douglas of Lothian.