Anglian kingdom of the 'Old North', covering roughly modern Northumberland, Tyne and Wear, Durham, and the Scottish Borders/East Lothian, stretching from the Forth to the Tees. Traditionally founded by Ida, who ruled from his stronghold at Bamburgh from around 547.
Merged with its southern neighbour Deira in the early 7th century (Æthelfrith's conquest c. 604 is the usual marker, though the union was contested and re-consolidated under Oswald after 634) to form the kingdom of Northumbria.
Standard scholarly survey of the individual Anglo-Saxon kingdoms, including Bernicia and Deira, and their (often legendary) founding traditions.