Isca Dumnoniorum 28 cities of Britain by the "History of the Britons" as Isca, although Ford read it as a reference to Penselwood and thought it more likely to be Lindinis (modern Ilchester). Isca was also known to the British as Caer Uisc but, after the Roman withdrawal from Britain around 410, there is very little evidence of habitation in Exeter for almost 300 years except for the remains of a building (possibly a church) in the area of the demolished forum and a few nearby graves dated to the 5th, 6th, and 7th centuries. After this, the historical record picks up
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,