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
Isca Augusta and timber ramparts of the fortress were strengthened by the addition of a stone revetment at the front. This "composite" rampart consisted of a stone wall 5 to 5½ feet thick, backed by a clay bank and fronted by a single ditch By 120 AD, detachments or vexillations of the legion were needed elsewhere in the province and Isca became more of a military base than a garrison. However, it is thought that each cohort still maintained a presence at the fortress. When Septimius Severus seized power in the 190s, he had Isca refurbished and the legion were in residence