Nanstallon in 1965 by Aileen Fox and Professor W. L. D. 'Bill' Ravenhill. Until recently (2007) it was the second Roman fort in Cornwall but following a geophysical survey another Roman fort has been found away near Restormel Castle. Constructed c. AD 55–60, Nanstallon fort is situated in mid Cornwall near the Fowey-Camel trade and communication route. Nanstallon was probably a forward operating base and was strategically well-placed for a Roman presence to be felt. However, the Roman Legion at Exeter was withdrawn c. AD 75 and with no Roman town west of Isca Dumnoniorum Cornwall settled down to four centuries
Isca Augusta legion was needed to repel a potential invasion from the Continent. The stone from Isca may have been used for building defences on the south coast. There may still have been an occasional military presence as late as the early 4th century, but the fortress was probably later taken over by the people of the surrounding vicus. The basilica of the baths was used as a cattle pen. Recent finds suggest Roman occupation of some kind as late as AD 380. According to the Gildas (followed by Bede), Roman Caerleon was the site of two early Christian martyrdoms in Britain,