Sir Alexander was the brother-in-law of Robert the Bruce who made him Chamberlain of Scotland in 1319-26. His seal appears on the letter dated 6 April 1320 to Pope John XXII, seeking recognition of Scotland’s political independence under the kingship of Robert the Bruce, known as the Declaration of Arbroath.

“For as long as but a hundred of us remain alive, never will we on any conditions be brought under English rule. It is not for glory, nor riches, nor honours that we are fighting, but for freedom — for that alone, which no honest man gives up but with life itself.”
- From The Declaration of Arbroath 1320.

Sir Alexander died at the Battle of Dupplin Moor which was fought in 1332 between supporters of the infant king, David II, and rebels supporting the Balliol claim to the Scottish throne.

The death of Robert the Bruce in 1329 left Scotland with a four-year-old king David II. David II (1325-1371) had a right to the throne solely because of the career and residual influence of his father. His claim to the throne was far from absolute and, from 1329 was challenged by Edward Balliol, son of John Balliol, John I of Scotland. The rebels were known as 'The Disinherited' due to the fact that they lost their land as a consequence of the Battle of Bannockburn in 1314.

The rebels and their English allies sailed from Hull to Kinghorn to get round the terms of the Treaty of Northampton that did not permit English forces to cross the Tweed. The two sides met at Dupplin Moor, Scone, some 5 miles (8 km) southwest of Perth on 10 & 11th August 1332. Forsaking the guerilla tactics of Bruce and Wallace, the Earl of Mar was drawn into a pitched battle against the rebels. In what would become a model for later English victories, the combined use of longbow archers and men-at-arms, supported by heavy cavalry, overcame the Scottish loyalists. Along with 2000 men at-arms, 70 knights and over 20 nobles, Donald the 8th Earl of Mar and Bruce's illegitimate son, Robert, were killed in the battle.

A stone cross, now in St. Serf's Church in Dunning, once marked the site of the battle.

David II was sent to France for his own safety in 1334, but Balliol was driven from Scotland a matter of months later. David returned to Scotland in 1341 and pursued a foreign policy largely in French interests.