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 Dumnoniorum the line between the Isca fortress and Topsham was excavated at the site on Topsham Road in 2010. Initial dating suggests that it was occupied at the same time as the Isca fortress, –75. The settlement () of Isca Dumnoniorum seems to have developed around the Roman fortress. It is one of the four cities () attributed to the Dumnonii by Claudius Ptolemy in his 2nd-century "Geography" and it served as the tribal capital () of the Dumnonii. It was also listed on the late-2nd century Antonine Itinerary, where it forms the southern terminus of route 15 () on the