Since the days of Henry II the English monarchy had intermittently claimed an overlordship of Scotland, based on the still earlier acknowledgment of Saxon overlordship by Scottish kings. King Edward, whose legal abilities were renowned, had already arbitrated in the Scottish succession. Since the alternatives were the splitting of Scotland into rival kingships or a civil war to decide the matter, the Scots were induced to seek Edward’s judgment; and he, pursuing all the time a path of strict legality, consented to the task only upon the prior condition of the reaffirmation of his overlordship, betokened by the surrender of certain Scottish castles.

Winston Churchill, A History of the English-Sp…, loc. 466