Underneath all the outward signs of prosperity during the Roman rule in Britain, there were causes at work which ensured the ruin of the province. The policy of centralization, and the very perfection of the machinery for government on autocratic principles, which brought about the destruction of the Roman Empire, as in our own days they have nearly ruined France, bore fruit in Britain in the helpless apathy of the provincials when the machinery was broken up. It is therefore no wonder that when the Roman garrison was finally withdrawn from this country, in the year 409, the provincials were left an easy prey to their enemies. Nor need we wonder that they set up isolated centres of government, which we may term communes, in the year 410, in which each city stood out for itself, instead of combining together for the common weal. From this time forward the inhabitants of the Roman province of Britain, severed from the Roman Empire, became a prey to the many tyrants who sprang up, and the anarchy followed so pathetically described by Gildas. It was at this time that the coinage became debased, and Roman coins afforded the patterns for the small bronze minimi of the Settle cave,[62] which are so abundant among the ruins of Roman cities in this country, such as St. Alban’s. The invaders of Britain must now be considered. The Picts and Scots had secured a rude liberty under the protection of their mountains and morasses, rather than by their success in arms against the Roman legions, and their raids into the Roman province had been curbed by the walls and lines of forts, extending, the one from the Firth of Forth to the Firth of Clyde, the other from the Solway Firth to the Tyne. In spite of these, however, from time to time, in the fourth century, they carried desolation into Northumberland and Yorkshire, even if they did not penetrate farther into the south. And on the withdrawal of the Roman legions, at the beginning of the fifth century, their raids were organized on a much larger scale. In the pages of Gildas we have a melancholy picture of their results. In the letter written to Ætius, the Roman commander in Gaul, in 446, the Britains are described as sheep, and the Picts and Scots as wolves. “The barbarians drive us back to the sea; the sea drives us back again to perish at the hands of the barbarians,” are the words put into the mouth of the embassy.[63] One plea for aid, which they advanced, is especially interesting, because it shows incidentally that the Roman civilization did not disappear with the withdrawal of the legions--the plea that unless they were succoured the name of Rome would be dishonoured. Nerved by despair, the British in the following year take up arms, and, according to Gildas, leave their houses and lands, and taking shelter in mountains and forests, and in caves,[64] succeed in driving back their Pictish and Scottish enemies.