of De Situ Albanie noted that: "The name Arregathel [Argyll] means margin of the Scots or Irish, because all Scots and Irish are generally called 'Gattheli'." Scotland came to possess a unity which transcended Gaelic, French and Germanic ethnic differences and by the end of the period, the Latin, French and English word "Scot" could be used for any subject of the Scottish king. Scotland's multilingual Scoto-Norman monarchs and mixed Gaelic and Scoto-Norman aristocracy all became part of the "Community of the Realm", in which ethnic differences were less divisive than in Ireland and Wales. This identity was defined in opposition to English attempts to annexe the country and as a result of social and cultural changes. The resulting antipathy towards England dominated Scottish foreign policy well into the fifteenth century, making it extremely difficult for Scottish kings like James III and James IV to pursue policies of peace towards their southern neighbour. In particular the Declaration of Arbroath asserted the ancient distinctiveness of Scotland in the face of English aggression, arguing that it was the role of the king to defend the independence of the community of Scotland. This document has been seen as the first "nationalist theory of sovereignty". The adoption of Middle Scots by the aristocracy has been seen as building a shared sense of national solidarity and culture between rulers and ruled, although the fact that north of the Tay Gaelic still dominated may have helped widen the cultural divide between highlands and lowlands. The national literature of Scotland created in the late medieval period employed legend and history in the service of the crown and nationalism, helping to foster a sense of national identity, at least within its elite audience. The epic poetic history of the Brus and Wallace helped outline a narrative of united struggle against the English enemy. Arthurian literature differed from conventional versions of the legend by treating Arthur as a villain and Mordred, the son of the king of the Picts, as a hero. The origin myth of the Scots, systematised by John of Fordun (c. 1320-c. 1384), traced their beginnings from the Greek prince Gathelus and his Egyptian wife Scota, allowing them to argue superiority over the English, who claimed their descent from the Trojans, who had been defeated by the Greeks. The image of St. Andrew, martyred while bound to an X-shaped cross, first appeared in the Scotland during