The Roman Era in Britain by John Ward

Politically, the Roman era in Britain began with the Claudian Conquest in A.D. 43, and ended with the isolation of the country from the rest of the decaying empire consequent upon the passing of northern Gaul into the hands of the Trans-Rhenish barbarians in A.D. 406-410. But Roman influence through intercourse with the Continent preceded the former event, and Britain continued to be Roman after the latter event, remaining so, harassed by foes from without and probably by dissensions within, until the English conquest.