[4] The life of William, Earl of Ross, is closely entwined with the political and military events of the reign of David II, who was ever vigilant to repel the English as they undertook to conquer Scotland.
David continued south into England where he was taken captive at the Battle of Neville's Cross near Durham for what turned out to be a period of eleven years.
[13] Upon David's return to Scotland, he imposed heavy taxation on his nobles in order to pay his ransom, a move which led to a rebellion of the Highland lords, including William and his half-brother, Hugh de Rarichies, in 1366.
His only son, William, was a sickly lad, and the earl was well aware that if the boy died, leaving him without a male heir, the earldom would pass out of the Mactaggart family.
To prevent this from coming to pass, he consulted with his sister Marjory, Countess of Caithness and Orkney, who consented to entailing the earldom to their half-brother, Hugh of Rarichies.
[16] Instead of agreeing that Hugh of Rarichies would succeed William, the king settled the earldom on William's daughter, Euphemia, and then forced her to marry Walter de Leslie, who had made a name for himself fighting with the king of France, with the Holy Roman Emperors in the Northern Crusades, and with Peter of Cyprus on his Alexandrian Crusade.
To this end, at Perth on 23 October 1370, David took the step of re-confirming William in the earldom of Ross and lordship of Skye, but only with the unwelcome stipulation that he must give his daughter in marriage to Leslie.