This thesis reports an investigation of Iron Age diet in Britain using carbon and nitrogen stable isotope data obtained from skeletal material from four locations across England and southern Scotland. Both human and animal bone Collagen has been analysed from Wetwang in East Yorkshire and other sites in East Lothian, Hampshire and Cornwall. Animal bone from Dorset has also been included. The aims of the study were to characterize British Iron Age diet in general isotopic terms and also to provide a contextual base for future analysis which allows an understanding of both inter- and intra-site variation in such data for this and other periods. The comparisons across the locations allowed consideration of geographical variability within England and southern Scotland and included material from coastal sites (Cornwall and East Lothian), from sites with easy access to rivers and estuaries (Hampshire) and an inland site where access to water would have been more difficult (Wetwang). All human groups were consuming high levels of animal protein and there was very little evidence for the consumption of aquatic resources. There was significant variation in 815N values between the locations, which was reflected both in the humans and the herbivores, such that it is likely to be related to environmental rather than to dietary differences. Intra-site group comparisons at Wetwang showed very little variation within the cemetery population IM according to age, sex, subjective status category or site phase. The data were very consistent within the populations, although those for Hampshire displayed more variation in nitrogen.