Dumnonia until they submitted to the See of Canterbury in the mid-9th century. Parish organisation was a later development of fully Normanised times. Around AD 55, the Romans established a legionary fortress at "Isca Dumnoniorum", modern Exeter, but west of Exeter the area remained largely un-Romanized. Most of Dumnonia is notable for its lack of a villa system, though there were substantial numbers south of Bath and around Ilchester, and for its many settlements that have survived from the Romano-British period. As in other Brythonic areas, Iron Age hillforts, such as Hembury and Cadbury Castle, were refortified in post-Roman times for
Celtic language decline in England England begin to be attested from around 670, pre-eminently in Anglo-Saxon charters; they have been intensively surveyed by the English and Scottish Place-Name Societies. Except in Cornwall, the vast majority of place-names in England are easily etymologised as Old English (or Old Norse, due to later Viking influence), demonstrating the dominance of English across post-Roman England. This has traditionally been seen as evidence for a cataclysmic cultural and demographic shift at the end of the Roman period, in which not only the Brittonic and Latin languages, but also Brittonic and Latin place-names, and even Brittonic- and Latin-speakers, were swept away.