April 2, 798. Battle at Whalley: Eardwulf of Northumbria defeats a conspiracy of his enemies
This battle, like the Battle of Edwin's Cliff fought by Æthelwold of Northumbria in 761 shortly after his accession, shows that being elected king of the Northumbrians in this age was not enough to ensure the loyalty of the people. In this context, while Æthelred's killings of his enemies in 791 and 792 look brutal from our vantage point, there were doubtless contemporaries who thought them simply well-judged pre-emptive strikes, avoiding the battles to establish effective supremacy that would otherwise be inevitable.
The Chronicle notes only that there was a great battle in Northumbria, on April 2, at Whalley (Lancs.) and that Alric, Heardberht's son, was killed, along with many others. Simeon of Durham as usual adds more details, suggesting that the battle was the result of a conspiracy formed by the murderers of King Æthelred, and joined by one Ealdorman Wada, and that after many had been killed on both sides Wada took to his heels, and Eardwulf royally won the victory. Wada may have fled to Coenwulf of Mercia, because he appears in connection with Coenwulf in a papal letter of 808 discussing the exile of Eardwulf (Haddan and Stubbs, Councils, III.563).