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 the isolation from the civilizing centres of the mainland and the consequent decay of commerce and culture—and we have ample explanation of the increasing difficulties of maintaining the old official unity of Britannia together with the final abandonment of the same.

Moreover, if the official unity of Britannia was impossible, much more so was any national unity of which it might have been capable, were it only for geographical reasons. Even officially it had apparently been found necessary to divide it into Prima and Secunda. A state west of a line drawn from the Dee to the Wiltshire Avon or thereabouts, divided as this territory is by the Severn Sea and exposed along the whole of its eastern boundary to hostilities from the English lowlands, was an absurdity. It tended to part asunder of itself. Sooner or later a strong attack from the east would capture the Severn shore from Gloucester to Bristol, which eventually took place in 577, the year of the Battle of Deorham by which Gloucester, Cirencester, and Bath fell into the hands of the West Saxons. Thus the unity of Roman Britannia became definitely a thing of the past. Henceforth Wales is free to evolve its own life. The unity of