 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 . 
