Question: Which battle taking place in 7th century England was the result of peace overtures from Augustine's English mission by the Synod of Chester where the armies of the combined Welsh kingdoms of Powys and Rhôs were virtually annihilated?
Sentence (from "Synod of Chester"): This led directly to the Battle of Chester, where Æthelfrith of Northumbria seems to have killed the kings of Powys and (possibly) Gwynedd during an attack on the ecclesiastical community at Bangor-on-Dee.
Relevant evidence: Yes