Margaret died in early October in Orkney on her way to Scotland, leaving the throne vacant. The Guardians called upon her fiancé's father, Edward I of England, to decide between various competitors for the Scottish throne in a process known as the Great Cause (Scottish Gaelic: An t-Adhbhar Mòr). One of the strongest claimants, John Balliol, Lord of Galloway, forged an alliance with the powerful Antony Bek, Bishop of Durham, the representative of Edward I in Scotland and began styling himself 'heir of Scotland', while another, Robert Bruce, 5th Lord of Annandale, turned up to the site of Margaret's supposed inauguration with a force of soldiers amidst rumours that his friends the Earl of Mar and the Earl of Atholl were also raising their forces. Scotland looked to be headed for civil war.
To avoid the catastrophe of open warfare between the Bruce and Balliol, the Guardians and other Scots magnates asked Edward I to intervene. Edward seized the occasion as an opportunity to gain something he had long desired—legal recognition that the realm of Scotland was held as a feudal dependency to the throne of England. The English kings had a long history of presuming an overlordship of Scotland, harking back to the late 12th century when Scotland had actually been a vassal state of England for 15 years from 1174 (Treaty of Falaise) until the Quitclaim of Canterbury (1189), but the legality of the 13th century claim was questionable. Alexander III, giving homage to Edward, had chosen his words very carefully: "I become your man for the lands I hold of you in the Kingdom of England for which I owe homage, saving my Kingdom" (author's italics).
In line with this desire, Edward demanded in May 1291 that his claim of feudal overlordship of Scotland be recognised before he would step in and act as arbiter. Indeed, he went so far as to demand that the Scots produce evidence to show that he was not the lawful overlord rather than presenting them with evidence that he was. The Scots' reply came that without a king there was no one in the realm responsible enough to possibly make such an admission, and so any assurances given by the Scots were worthless. Although technically and legally correct by the standards of the time, this reply infuriated Edward enough that he refused to have it entered on the official record of the proceedings.
The Guardians and the claimants still needed Edward's help, and he did manage to press them into accepting a number of lesser though still important terms. The majority of the competitors and the Guardians did eventually step forward to acknowledge Edward as their rightful overlord, even though they could not be taken as speaking for the realm as a whole. They also agreed to put Edward in temporary control of the principal royal castles of Scotland despite the castles in question not being theirs to give away. For his part, Edward agreed that he would return control of both kingdom and castles to the successful claimant within two months. In the ongoing negotiations between the two countries, the Scots continued to use the Treaty of Birgham as a reference point, indicating that they still wished to see Scotland retain an independent identity from England.
Having got these concessions, Edward arranged for a court to be set up to decide which of the claimants should inherit the throne. It consisted of 104 auditors plus Edward himself as president. Edward chose 24 of the auditors while the two claimants with the strongest cases—Bruce and Balliol—were allowed to appoint forty each.