Aldfrith's Northumbria
Bede, paraphrasing Virgil, wrote that following Ecgfrith's death, "the hopes and strengths of the English realm began 'to waver and slip backward ever lower'". The Northumbrians never regained the dominance of central Britain lost in 679, or of northern Britain lost in 685. Nonetheless, Northumbria remained one of the most powerful states of Britain and Ireland well into the Viking Age.
Aldfrith ruled both Bernicia and Deira throughout his reign, but the two parts remained distinct, and would again be divided by the Vikings in the late ninth century. The centre of Bernicia lay in the region around the later Anglo-Scottish border, with Lindisfarne, Hexham, Bamburgh, and Yeavering being important religious and royal centres. Even after Ecgfrith's death, Bernicia included much of modern southeast Scotland, with a presumed royal centre at Dunbar, and religious centres at Coldingham and Melrose. The details of the early Middle Ages in northwest England and southwest Scotland are more obscure, but a Bishop of Whithorn is known from shortly after Aldfrith's reign. York, Catterick, Ripon, and Whitby appear to have been important sites in Deira.
Northumbria's southern frontier with Mercia ran across England, from the Humber in the east, following the River Ouse and the River Don, to the Mersey in the west. Some archaeological evidence, the Roman Rig dyke, near modern Sheffield, appears to show that it was a defended border, with large earthworks set back from the frontier. The Nico Ditch, to the south of modern Manchester, has been cited in this context, though it has also been argued that it was simply a boundary marker without fortifications. In the far north, the evidence is less clear, and it appears that authority lay with sub-kings, perhaps including native British rulers. The family of Ecgfrith's general Berht may have been one such dynasty of under-kings.
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