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 9th 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.