 Oswald and Oswiu returned to Northumbria after Edwin 's death in 633 , and between them they ruled for much of the middle of the 7th century . The 8th @-@ century monk and chronicler Bede lists both Oswald and Oswiu as having held imperium , or overlordship , over the other Anglo @-@ Saxon kingdoms ; in Oswiu 's case his dominance extended beyond the Anglo @-@ Saxons to the Picts , the Gaels of Dál Riata , and the many obscure and nameless native British kingdoms in what are now North West England and southern Scotland . Oswiu 's overlordship was ended in 658 by the rise of Wulfhere of Mercia , but his reign continued until his death in 670 , when Ecgfrith , one of his sons by his second wife , Eanflæd , succeeded him . Ecgfrith was unable to recover Oswiu 's position in Mercia and the southern kingdoms , and was defeated by Wulfhere 's brother Æthelred in a battle on the River Trent in 679 . 
