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 "Battle of Chester"): Æthelfrith of Northumbria annihilated a combined force from the Welsh kingdoms of Powys, Rhôs (a cantref of the Kingdom of Gwynedd) and possibly Mercia.
Relevant evidence: Yes