of the name Yeavering, which looks deceptively English, back to the British gafr from Bede's mention of a township called Gefrin in the same area. Yeavering continued to be an important political centre after the Anglo-Saxons began settling in the north, as King Edwin had a royal palace at Yeavering. Overall, English place-names dominate the Northumbrian landscape, suggesting the prevalence of an Anglo-Saxon elite culture by the time that Bede – Anglo-Saxon England's most prominent historian – was writing in the eighth century. According to Bede, the Angles predominated Germanic immigrants, who settled north of the Humber and gained political prominence during this time period. While the British natives may have partially assimilated into the Northumbrian political structure, relatively contemporary textual sources such as Bede's Ecclesiastical History of the English People depict relations between Northumbrians and the British as fraught. Unification of Bernicia and Deira The Anglo-Saxon countries of Bernicia and Deira were often in conflict before their eventual semi-permanent unification in 654. Political power in Deira was concentrated in the East Riding of Yorkshire, which included York, the North York Moors, and the Vale of York. The political heartlands of Bernicia were the areas around Bamburgh and Lindisfarne, Monkwearmouth and Jarrow, and in Cumbria, west of the Pennines in the area around Carlisle. The name that these two countries eventually united under, Northumbria, may have been coined by Bede and made popular through his Ecclesiastical History of the English People. Information on the early royal genealogies for Bernicia and Deira comes from Bede's Ecclesiastical History of the English People and Welsh chronicler Nennius’ Historia Brittonum. According to Nennius, the Bernician royal line begins with Ida, son of Eoppa. Ida reigned for twelve years (beginning in 547) and was able to annex Bamburgh to Bernicia. In Nennius' genealogy of Deira, a king named Soemil was the first to separate Bernicia and Deira, which could mean that he wrested the kingdom of Deira from the native British. The date of this supposed separation is unknown. The first Deiran king to make an appearance in Bede's Historia Ecclesiastica Gentis Anglorum is Ælle, the father of the first Christian Northumbrian king Edwin. A king of Bernicia, Ida's grandson Æthelfrith, was the first ruler to unite the two polities under his rule. He exiled the Deiran Edwin to the court of King Rædwald of the East Angles in order to claim both kingdoms, but