The earliest written documentation of Arthur is given to us by a 9th Century monk who went by the name of Nennius. Nennius wrote Historia Brittonum, The History of the Britons. It is not an easy read. Structure and organisation were two words Nennius chose to ignore. But it is worth persevering with his work, because there are some real gems in there.
What I love about the work of Nennius is how he portrays Arthur. Think of a Dark Age version of Iron Man and you might be getting somewhere. Strangely however, he does not describe Arthur as a king. See what you think?
Arthur, whoever he was, had captured the imagination of a nation and in later works he became the hero that we all know and love.