Tall, pale and thoughtful, Pembroke has been described as ‘a man of modest talents’. A moderate figure among the English nobles, he arrested Edward's favourite Piers Gaveston in 1312, but when other lords killed Gaveston he became a steadfast supporter of the king, both on and off the battlefield.
An experienced military commander and brother-in-law of Bruce's rival John Comyn, in 1306 he had been made Guardian of Scotland and defeated Bruce at the Battle of Methven. However, the following year he retreated from Bruce at the Battle of Loudoun Hill and resigned as guardian.
At Bannockburn, Pembroke’s company numbered about eighty cavalry. He stayed close to the king’s side, and when it became clear that all was lost, he led the king away from the battle. Many of Pembroke’s men were killed as they fled, including his nephew John Comyn 'the Younger'.
Pembroke tried without much success to keep the peace between Edward and his unruly barons after Bannockburn. He collapsed and died while on a diplomatic mission in France in 1324.