Beyond the peripheral zone of coin-issuing tribes - the Durotriges, Dobunni and Corieltauvi - lay vast expanses of Britain: the south-western peninsula, Wales and the north. The south-west differed from the rest in that it remained in contact by sea with both the south-eastern tribes and with Armorica and thus absorbed cultural influences from both. Wales and the north on the other hand were far removed from the rapidly expanding economies of the south-east and were largely isolated from Continental influences until the second half of the first century AD by which time Roman rule, or the bow-wave effects of the Roman presence, had penetrated all but the extreme north-west. For these reasons there is a considerable degree of cultural unity over large stretches ofcountry and it is sometimes difficult to isolate material of the Late Iron Age from that of earlier periods. Nevertheless the writings of several Roman authors provide a valuable descriptive horizon from which to assess the social and economic changes of the preceding decades.