The third volume in the Society's series on this major late "Iron Age and Roman" site. Excavations on the site of the forum basilica of the civitas capital of Calleva Atrebatum have produced the first substantial evidence of the layout and character of the late Iron Age oppidum. In addition to the structural evidence, major assemblages of late Iron Age coins, ceramics, metalwork, faunal and other environmental data are reported on. This report also describes and analyses the major pre-Flavian, timber courtyard building and Flavian timber basilica, which were sealed beneath the foundations of the Hadrianic-Antonine successor as well as their associated, finds. It concludes with new evidence for the plan of the latter and of the latest Roman industrial occupation of the building.