628. Penda of Mercia defeats Cynegils and Cwichelm of Wessex at Cirencester
This battle, a Mercian victory in the territory of the Hwicce, may signal the beginnings of Hwiccian dependence on the more powerful rulers of the Mercians, though clear evidence of this subordinate relationship does not appear until the 670s (see entry on c.670-c.790).
Bede notes that Penda's sister was married to Cenwealh, the son of Cynegils (HE, iii.7); since Cenwealh later repudiated his wife (see entry on 645), it may be that the match was forced upon him. The peace settlement after the battle in 628 (the Chronicle notes that Penda and Cynegils and Cwichelm came to terms) would be a plausible context.