Æthelhere of East Anglia is an interesting figure. He was the brother and successor of King Anna son of Enni. He had a one year reign from c. 654 to November 655, when Bede specifically says that he died at the battle of Winwæd.
“The battle was joined and the heathen were put to flight or destroyed; of the thirty royal ealdormen who had come to Penda’s help nearly all were killed. Among them was Æthelhere, brother and successor to Anna, king of the East Angles and the cause of the war; he was cut down, having suffered the loss of all his thegns and followers. The battle was fought near the river Winwæd, which owing to heavy rains, had overflowed its channels and its banks to such an extent that many more were drowned in flight than were destroyed by the sword in battle.” (HE III.24, McClure & Collins, 1994:150)
This translation crediting the cause of the war to Æthelhere has been challenged. McClure and Collins (1994: 396) note that Prestwich saw it as beginning a new sentence and referring to Penda. This really doesn’t make sense though. Penda was clearly the leader of his forces, why go on to state that he was the ‘author of the war’? It has been noted elsewhere that Bede doesn’t give Penda the usual regnal summary or even specifically say that he died in the battle. This ambiguity makes Prestwich’s reading more tempting. However, the Liber Eliensis specifically contradicts this; it specifically says that Æthelhere instigated the war. “Amongst the slain was the very person who instigated the war, Æthelhere, the brother of Anna, king of East Angles, who became ruler in succession of him.” From this is it clear that the author of the LE read his copy of Bede’s History in such a way to make his own East Anglian king the cause or instigator of the war. So even in an East Anglian royal monastery there was no tradition to contradict this interpretation.
It seems very likely that Penda’s campaign into Northumbria in 655 was directly related to his war against Anna of East Anglia. Æthelhere would not be the first royal brother to turn to a traditional enemy to assist him in coming to the throne. His successor Æthelwold was a supporter of Lindisfarne’s missionaries, Bishop Cedd among the East Saxons. Æthelwold stood as godfather to King Swithelm of Essex, as his brother Anna had stood as godfather to Cenwealh of Wessex. It is unclear who baptized Cenwealh, uncharacteristically Bede doesn’t tell us. The Liber Eliensis claims that he was baptized, not surprisingly, by Bishop Felix who had come to East Anglia when Sigiberht returned from exile. Archbishop Honorius of Canterbury ordained a Bishop Berhtgisl (Boniface) of Kent for East Anglia before his death in September 653 (Bede, HE III:20), a year before the death of King Anna. McClure and Collins note that he remains bishop of East Anglia until 670. Experiencing a king who was willing to ally himself with pagan king Penda in a grab for power may have made Berhtgisl much more willing to cooperate with Lindisfarne if that alliance brought stability.
Anyway, it is clear that there was a close alliance between Bernicia and East Anglia before and after the death of King Anna. The strength of an alliance with King Anna is surely what made Æthelthryth an attractive bride for the much younger prince Ecgfrith. Æthelthryth and Ecgfrith were married in c. 661, during King Æthelwold’s reign (655-663) when Ecgfrith was only 15; presumably the marriage took place as soon as he was deemed old enough. Æthelwold was succeeded by his nephew Ealdwulf who reigned for nearly two generations (663-713). The succession of a nephew whose father had never been king (that we know of) might suggest that pleasing Northumbria was a factor in his succession. As the nephew of St Hild, he was also a matrilineal cousin of Queen Eanflaed of Northumbria. The year after Ealdwulf succeeded, King Oswiu of Northumbria took part in nominating the next Archbishop of Canterbury. Such close ties between Northumbria and East Anglia may explain the lengths that Mercian kings Æthelbald and Offa went to secure their hegemony over East Anglia in the next century.