Clan Sinclair to St Briavels Castle, and in 1296 he swore fealty to Edward I of England. In 1303 the Battle of Roslin took place where Scots under Henry Sinclair of Rosslyn and the Clan Comyn defeated an English force. The Battle of Loudoun Hill took place in 1307 where Scots under Robert the Bruce, assisted by Henry Sinclair of Rosslyn again defeated the English. The family initially favoured John Balliol's claim to the throne but later it became paramount that they gave their loyalty to Robert the Bruce. The Battle of Bannockburn was fought in 1314, where the Clan Sinclair fought
Robert the Bruce appear not to have expected the Scots to give battle here, and as a result had kept their forces in marching, rather than battle, order, with the archers − who would usually have been used to break up enemy spear formations − at the back, rather than the front, of the army. The English cavalry found it hard to operate in the cramped terrain and were crushed by Robert's spearmen. The English army was overwhelmed and its leaders were unable to regain control. Edward II was dragged from the battlefield, hotly pursued by the Scottish forces, and only just escaped