[2] He was chosen as an auditor at the trial between John Balliol and Robert Bruce, when they competed before Edward to decide who would take the throne of Scotland.

William was one of the leaders of the Scottish army at the Battle of Dunbar in 1296, when Edward invaded Scotland to punish John Balliol for refusing to support the English invasion of France.

After the Scottish defeat, he was captured by the English and sent to the Tower of London, where he remained until September 1303, when an order was issued for his escort to Scotland.

[2] In 1306, Robert's wife Elizabeth, his daughter Marjorie, and other Bruce supporters took refuge from the advancing English army in the chapel of St Duthac at Tain in Ross, while on their way to the safety of Orkney.

He had married a lady named Euphemia, who was likely the daughter of Sir Hugh de Berkeley, Justiciar of Lothian.