616. Battle at the river Idle: Rædwald of the East Angles kills Æthelfrith of Northumbria
Edwin succeeds to Northumbria
The story of Rædwald's alliance with Edwin is told by Bede as part of the long account of Edwin's conversion (HE, ii.12). Edwin of Deira was in exile from Æthelfrith of Bernicia, and had been wandering for long years through all the kingdoms of Britain when he sought protection from Rædwald of the East Angles. Rædwald took Edwin in and promised to protect him. When Æthelfrith learnt that Edwin was in East Anglia, he sent messengers to Rædwald promising large amounts of money if he would put Edwin to death. Rædwald refused, and so Æthelfrith sent a second and a third time, promising even larger gifts and threatening war if Rædwald refused. Finally, either corrupted by the bribes or cowed by the threats, Rædwald agreed and promised either to kill Edwin or give him up to the Bernician messengers. Edwin learned this and went to sit outside the hall, where a heavenly messenger came to give him hope; shortly after that, a faithful friend sought him out, to tell him that Rædwald's wife had convinced him that going against his initial promise to Edwin would have been entirely unbecoming and a sacrifice of his honour. Rædwald sent away Æthelfrith's messengers, and shortly afterwards gathered together a large army to restore Edwin to the Northumbrian throne. Rædwald's army met Æthelfrith's without giving the Northumbrian king time to prepare, and Æthelfrith was slain in the battle on the Mercian border on the east bank of the river Idle, as was Rædwald's own son Regenhere. It was this battle that enabled Edwin to succeed to the Northumbrian throne.
The Anglo-Saxon Chronicle records the battle under 617, but since Bede says that Edwin had ruled the Northumbrians for 17 years at the time of the Battle of Hatfield of October 12, 633 (HE, ii.20), the correct date for the battle and for Edwin's accession is presumably 616.