After Queen Mary's husband, Lord Darnley, was murdered by suspected agents of the Queen, Captain Thomas planned the assault and led a small force of 150 men in 1571 that scaled the cliffs and embattlements to expell the castlegarrison loyal to Catholic Queen Mary from Dumbarton Castle. Two years later he led the siege and received the surrender of Edinburgh Castle. This eliminated the final barrier to a reunification of Scotland under Queen Mary's son, ProtestantKing James, in 1573. His lineage became known as Crawford of Jordanhill, his estate in the present-day suburbs of Glasgow. Captain Thomas is entombed at KilbirnieKirk where the photo of his tomb marker on the right identifies his final resting place.