Although the English invasion of Britain is by far the most important of all those which have affected the island, it is impossible to focus any very clearly defined picture of the happenings during the long period of nearly two centuries that followed the so-called departure of the Romans. The picture is blurred, but certain strong outlines are conspicuous, and in this chapter an attempt has been made to concentrate attention on these salient features. The incident which led to the English invaders obtaining a secure foothold in south-east Britain was probably connected with internal troubles rather than foreign invasions. The Celtic chieftains of the south-west were less occupied than their northern contemporaries in repelling foreign invaders. They must have cast longing eyes upon the wealthy Romanized cities, and cherished hopes of bringing them, or some of them, under their sway. Vortigern, one of these rulers, probably prince of the Silures, seems to have partially succeeded in doing so, and about A.D. 450 appears as supreme over the south as far as Dover Straits. Whether his suzerainty extended north of the Thames must be considered very doubtful. The ‘Historia Brittonum’ describes the situation as follows: ‘After the above-said war, the assassination of their rulers, and the victory of Maximus, who slew Gratian, _and the termination of the Roman power in Britain, they were in alarm forty years_. Vortigern then reigned in Britain, and in his time the people had cause of dread, not only from the inroads of the Picts and Scots, _but also from the Romans, and their apprehensions of Ambrosius_.’