While still Lord Kilmaurs, this nobleman was one of the principal adherents of the English Court in Scotland, and accepted a pension from King Henry VIII.
He was one of the party which joined the force of the Earls of Arran and Lennox on 23 November 1524, when they took possession of Edinburgh, and endeavoured to withdraw the young king James V from the Queen Mother.
In 1538 he accompanied David Bethune, Bishop of Mirepoix, afterwards a celebrated cardinal, to France to conclude a treaty for James V's marriage with Mary of Guise.
In 1542 the earl was taken prisoner by the English at the Battle of Solway Moss and committed to the custody of the Duke of Norfolk, but was released on payment of a ransom of a thousand pounds and subscribing by his own hand to support Henry VIII's project of a marriage between the young Prince Edward and the Scottish Queen.
[2] Allied with the Earl of Lennox in 1544 he was, with his 500 vassals as spearmen, attacked on Glasgow Muir by Regent Arran and defeated "with great slaughter", his second son amongst the slain.