But Constantine made a much greater change with regard to religion by the establishment of Christianity. At what time the Gospel was first preached in this island I believe it impossible to ascertain, as it came in gradually, and without, or rather contrary to, public authority. It was most probably first introduced among the legionary soldiers; for we find St. Alban, the first British martyr, to have been of that body. As it was introduced privately, so its growth was for a long time insensible; but it shot up at length with great vigor, and spread itself widely, at first under the favor of Constantius and the protection of Helena, and at length under the establishment of Constantine. From this time it is to be considered as the ruling religion; though heathenism subsisted long after, and at last expired imperceptibly, and with as little noise as Christianity had been at first introduced.
In this state, with regard to the civil, military, and religious establishment, Britain, remained without any change, and at intervals in a tolerable state of repose, until the reign of Valentinian. Then it was attacked all at once with incredible fury and success, and as it were in concert, by a number of barbarous nations. The principal of these were the Scots, a people of ancient settlement in Ireland, and who had thence been transplanted into the northern part of Britain, which afterwards derived its name from that colony. The Scots of both nations united with the Picts to fall upon the Roman province. To these were added the piratical Saxons, who issued from the mouths of the Rhine. For some years they met but slight resistance, and made a most miserable havoc, until the famous Count Theodosius was sent to the relief of Britain,--who, by an admirable conduct in war, and as vigorous application to the cure of domestic disorders, for a time freed the country from its enemies and oppressors, and having driven the Picts and Scots into the barren extremity of the island, he shut and barred them in with a new wall, advanced as far as the remotest of the former, and, what had hitherto been imprudently neglected, he erected the intermediate space into a Roman province, and a regular government, under the name of Valentia. But this was only a momentary relief. The Empire was perishing by the vices of its constitution.