670AD. Aelfwine the younger son of Oswiu became sub king of Deira at the age of nine, when his brother Ecgfrith took the throne of Northumbria at the death of his father Oswiu.
679AD.At the age of eighteen, Aelfwine joined his forces with the army of Ecgfrith and they marched to do battle with the army of King Aethelred of Mercia. The battle took place near the River Trent in Lindsey, Ecgfrith was defeated and Lidsey came back under Mercian control.
Aelfwine then 18 year old, was killed in the battle fighting alongside his brother, and because of his death there was a great fear that the conflict between the Mercians and the Northumbrians would esculate beyond control. However, after the intervention of Archbishop Theodore, things were smoothed over and weregilt was paid by Aethelred to Ecgfrith, in compensation for the death of his brother.
After Aelfwine's death, Deira was absorbed by Northumbria and ceased to exist as a kingdom.
