Eadwine, a member of the royal line of Deira who had spent his early life in exile, acceded to the throne of Northumbria with the help of the East Anglian king Rædwald. Initially controlling the province of Deira only, Eadwine soon expanded his power base, and was described by Bede as one of seven overkings of Britain.
Ahern, Eoghan. "Eadwine appointed King of Northumbria". The Literary Encyclopedia. First published 12 April 2016
[http://www.litencyc.com/php/stopics.php?rec=true&UID=1920, accessed 25 June 2016.]