Rome gave up on Britain after years of strife with the locals, but also because the central government in Rome was crumbling. In the early years of the 400s, Britain was barely able to sigh with relief to see the backs of the Romans when the pagan invaders of Angles, Saxons, and Jutes from Germany (Saxony) and Denmark started arriving, raiding, enslaving, and eventually staying in the abandoned Roman settlements. It was a rough go. Christianity had yet to take hold on the sceptered isle. We see the pagan influence of these raiders even today through our days of the week: the gods Tiw, Woden, Thor, and Friya give us four days, and then the moon and sun have theirs. The last of the Roman influence--Saturn--gets one, too. Slowly, the hand-to-mouth existance got better and the isle became known as Angle-land, where the people spoke Anglo-Saxon (or Old English), giving us such written works as Beowulf.
Next time: St. Patrick and Christianity