This book outlines the discovery and investigation of a Roman fort, enclosing an area of c. 2.1 ha, which overlooks the River Tamar, at Calstock in south-east Cornwall. Extensive geophysical survey has taken place, alongside campaigns of evaluation trenching and area excavation between 2007 and 2010. The fort was established c. AD50/55, and continued in use until c. AD 75/85. The presence of an earlier marching camp is also proposed. The whole site appears to be surrounded by a large polygonal hilltop enclosure that may have Iron Age origins, though may alternatively be of Roman military construction. Activity during the medieval period recommences by the eighth century, with two major phases of timber building in the eleventh / twelfth and twelfth / thirteenth centuries. The parish church of St Andrew sits within the footprint of the fort, and associated burial grounds overlay the northern half of the site.The contexts of Roman military and medieval occupation are discussed within the regional and national context.