Kingdom of Dumnonia

Dumnonia was a Brythonic kingdom in the western part of sub-Roman Britain, covering present-day Devon, Cornwall and parts of Somerset. Its name derives from the Dumnonii, a tribe recorded in the Roman period, and its rulers appear in early Welsh genealogies and saints' lives. The kingdom emerges into clearer light in the sixth and seventh centuries, when its kings fought the expanding Anglo-Saxon kingdom of Wessex. Battles at Peonnum and elsewhere pushed its frontier westward, and by the late seventh century much of Somerset and Devon had passed to Wessex. The Cornish branch retained independence longer, resisting until Ecgberht of Wessex campaigned in Cornwall in 838. A final expulsion of the Britons from Exeter is associated with Æthelstan around 927, although Cornish distinctiveness survived. Dumnonia was a Christian polity with monastic centres such as Bodmin and Glasney, and it maintained links with Brittany and Ireland across the Celtic Sea. Its language, Southwestern Brittonic, was the ancestor of Cornish.