Four years before the death of Thorlogh O'Brien, a Prince destined to be the life-long rival of his great son, had succeeded to the kingship of the northern tribes. This was Donald, son of Ardgall, Prince of Aileach, sometimes called "O" and sometimes "Mac" Laughlin. Donald had reached the mature age of forty when he succeeded in the course of nature to his father, Ardgall, and was admitted the first man of the North, not only in station but for personal graces and accomplishments; for wisdom, wealth, liberality, and love of military adventure.