When Aulus Plautius founded the Fosse frontier in the years AD 44-7 he was simply emphasizing a geographical and political truth. Britain could be divided into two parts about a line drawn along the Jurassic ridge from Lincoln to Lyme Bay. To the south and east lay a densely settled region with authority centralized about oppida and with a subsistence economy depending to a large extent on the production ofgrain. To the north and west settlement was more scattered and in places sparse, there was little centralization of power and, while cereals were widely grown, there appears to have been a greater reliance on stock rearing. To the Roman military mind the south-east was clearly the part to become a province, for grain was an immensely valuable commodity and arable farmers, because of their dependence upon the seasons, were sedentary and thus easier to control. Admittedly, Plautius was seeing Iron Age Britain at its most developed, after a 150 years or more of close contact with the Continent, but this basic geographical divide was equally relevant in the earlier period and played a considerable part in influencing the form, density and the distribution of settlements.