Edwin added Scottish and Welsh territory to this kingdom and established its superiority in England.  
It was originally composed of two independent kingdoms which were separated by the Tees River.  It was united by Aethelfrith of Bernicia, who was later defeated by Edwin of Deira  Edwin added Scottish and Welsh territory to this kingdom and established its superiority in England.  The Danes invaded it in 867 with their victory at York, and Canute installed Danish earls, of whom Siward was the last and most powerful  FTP, name this kingdom of northern England.
It was originally composed of two independent kingdoms which were separated by the Tees River.  
Northumbria