According to Lockhart family tradition, he accompanied Sir James Douglas in their curtailed attempt to carry the heart of Robert the Bruce to the Holy Land in 1330.
[1] Following the death of Robert the Bruce in 1329, his companion Sir James Douglas (aka the "Black Douglas"), set out to fulfil the King's last wish, that his heart be taken to the Holy Land, to be deposited in the Holy Sepulchre at Jerusalem.
It is claimed by a Lockhart family historian that Sir Symon Locard was entrusted with the key: “In 1329 a band of Scottish knights set out to fulfil the last wish of their dead King.
Their leader, Lord James Douglas, carried the King's heart in ‘ane cas of silver fyn, enamilit throu subtilite’ hung about his neck.
Sir Symon had won fame and distinction in the wars against the English; and now he was entrusted with the key of the precious casket.”.