William was the Armour bearer and aide to Robert the Bruce. The Irvines had been close allies of the Bruce during his wars with England. During one such time the Bruce made flight with a few aides, riding hard and exhuastingly. At one point they had to rest and the Bruce took sleep under a holly tree while William Irvine kept guard. From this story grows the Irvines of Drum Castles coat of arms with the holly. At the Battle of Bannockburn (where the Scots won) in June 1314 William fought alongside the Bruce.