There was first, on the site occupied by the present castle, a camp of about ten acres, probably constructed after the conquest of the Silures A.D.
He subdued the Silures, and held the other native tribes in check till he was superseded by Agricola (78).
In Roman times the eastern half of the county formed part of the territory of the Silures, a pre-Celtic race, whose governing class at that time probably consisted of Brythonic Celts.
Its massive Roman walls still survive, and recent excavations have revealed a town hall and market square, a temple, baths, amphitheatre, and many comfortable houses with mosaics, &c. An inscription shows that under the Roman Empire it was the chef-lieu of the Silures, whose ordo or county council provided for the local government of the district.
On the advance of Ostorius into western Britain, he met with considerable resistance from Caractacus (Caradog), king of the Silures, but after some encounters this prince was eventually captured and sent in chains to Rome.