Towards the middle of the 8th century Strathclyde was again threatened by an alliance between the Northumbrians and Picts, and in 750 the Northumbrian king Eadberht wrested from them a considerable part of their territories in the west including Kyle in Ayrshire.
There may be the folk-right of West and East Saxons, of East Angles, of Kentish men, Mercians, Northumbrians, Danes, Welshmen, and these main folk-right divisions remain even when tribal kingdoms disappear and the people is concentrated in one or two realms. The chief centres for the formulation and application of folkright were in the 10th and iith centuries the shire-moots, while the witan of the realm generally placed themselves on the higher ground of State expediency, although occasionally using folkright ideas.
But in 957 the Mercians and Northumbrians revolted and chose Edgar as their king.
He succeeded his brother Edmund in the year 946 and at this time received the formal submission both of the Northumbrians and Scots.
The latter had just crossed from Ireland and had been chosen king by the Northumbrians, who threw off their allegiance to Edmund.
It is notable that when, after Edreds death, there was civil strife, owing to the quarrel of his nephew Edwy with some of his kinsmen, ministers and bishops, the rebels, who included the majority of the Mercians and Northumbrians, set up as their pretender to the throne not a Dane but Edwys younger brother Edgar, who ruled for a short time north of Thames, and became sole monarch on the death of his unfortunate kinsman.
Edwin and Morcar, who should have been at his side with their Mercians and Northumbrians, were still far awayprobably from treachery, slackness and jealousy.
He refused to allow his kingdom to remain in dependence on the Irish Dalriada, but coming into collision with his southern neighbours he led a large force against .Ã† thelfrith, king of the Northumbrians, and was defeated at a place called Daegsanstane, probably in Liddesdale.