Stewart was an infant when his father died and inherited his estates and titles in Berwickshire, Abernethy and Angus.
(St Clair was slain in 1330, along with Sir James Douglas, at the Battle of Teba whilst accompanying King Robert's Heart to the Holy Land.)
The petition for this marriage was sent to the Holy See, with support from John II of France, which would suggest that the young Angus spent time at the French court.
[2] Present at the siege of Berwick in 1355, Angus was one of the lords that negotiated the release of David II following his 10-year captivity following the Battle of Neville's Cross.
[4] Angus was considered one of the conspirators in the murder of King David's mistress, Catherine Mortimer, at Soutra in 1360, and was duly imprisoned.