The indigenous population of the British isles were Celtic peoples such as the Picts in the north of what is now Scotland, and various tribes of Britons. In the year 43 AD, the southern part of Britain (without most of what is now Scotland) was invaded by the Romans and integrated into their expanding empire. The Romans retained control of much of Britain until they withdrew in the year 410, leaving the Britons to fend for themselves and defend against attack from the Picts in the North and the Irish in the west. It was at this time that Germanic peoples living in what is now northern Germany, Denmark and the Netherlands, known collectively as "Anglo-Saxons", migrated across the North Sea and settled the eastern half of Britain, bringing with them Germanic languages and dialects which over time developed into what we recognise as "English". King Arthur, who may have been legendary figure, was possibly a leader of the post-Roman Britons as they sought, unsuccessful...