BY the end of the first century AD most of the lands occupied by the Celtic peoples south of the Rhine-Danube line were under Roman occupation. To the north of the Danube the Celtic territories of Bohemia and Moravia had become Germanic, while further east in the Great Hungarian Plain and Transylvania the Celtic enclaves had been absorbed either within the Dacian state or by the incoming Sarmatian tribes. It was only along the extreme north-western periphery, in north and west Scotland and in Ireland, that Celtic-speaking communities continued to exist without the benefit of romanization.
The treatment of native Celtic societies by Roman administrators varied from region to region, but for the most part the newly imposed structures made good use of indigenous systems. Thus in Gaul the Augustan reorganization which divided the country beyond the Province (now Gallia Narbonensis) into Aquitania, Gallia Lugdunensis, and Gallia Belgica was reflecting directly the ethnic divides noted by Caesar when he distinguished between the Aquitanians, the Celts, and the Belgae. Below this tier of administration lay the individual civitates, which, almost invariably, were directly, or closely, related to existing tribal divisions, allowing much of the economic, social, and legislative structure of the indigenous systems to remain in place. Those native towns which were well sited to become nodes on the newly imposed road system simply continued, while others in less favourable locations withered away to be replaced by new towns: Bibracte gave way to Autun and Villeneuve to Soissons in the Augustan period.
In the south-east of Britain the situation was much the same, though in the early stages of the occupation two large tribal units were left under the direct control of client kings. In East Anglia the Iceni were ruled by Prasutagus until