There's been a sixth-century slate found in Cornwall, reading Artognou, father of a descendant of Coll, has had this built. An Arthur? The Arthur? Many historians feel it can't be so, since otherwise, any mentions of Arthurs are from the 12th century.
Why would that be?
The first recorded Arthurian stories are in the Mabinogian and a few other sources. These were greatly expanded upon later. Arthurianism hit its heyday in the late thirteenth and early 14th Centuries.
The most probably "real" Arthur would be a Dark Ages King after the fall of Rome and the departure of the Legions. Some feel he may have been a Romano Brit, others think he may have been Welsh or Cornish. Either way, he was certainly born in England and his ancestry would likely have been somewhat mixed.
David Drake writes in "The Dragon Lord" that when he was doing research for that book he discovered a generation during which all the Saxons and the Angles attempting to invade Britain came back with bloody noses and their tails between their legs. During that period SOMEONE was kicking butt and taking names and keeping the invaders out. Was this the person who founded the legends of King Arthur? Quite possibly.
The legends are enduring and common enough that there is fair reason to believe that there is some basis for reality. However, Arthurian scholars will tell you that "All that sex? That was the French." Lancelot and Galahad do not appear at all in the original Welsh tales although "Menuw the Magician" (Merlin) does as do Kei (sometimes spelled Cei or Kay), Bedewyr and Gawain. Tristan and Ysolte is also an ancient tale and may, or may not (probably not) have had any commonality with the Arthurian legends. My guess is that it's a separate tale that was bound in for enhanced storytelling.
So - in closing - I do believe there was probably a "real person" providing the kernel of truth the legend is based on. But he'd have been a regular guy trying to keep out the invaders. It seems likely that he held things together enough for Briton to have a brief, one generational, "Golden Age" during which peace prevailed. In the end, of course, this ended with waves of Saxons and Angles and Danes sweeping in to intermingle and absorb the native tribes. By the time of the Norman Conquest England was "Anglo-Saxon" and no trace of Roman influence seems to remain at all save for a few linguistic leftovers in the language. The culture is pretty much solidly invader and little recognizable remains of the old Roman Briton at all.
Silver Warder
Warder to Rebelaessedai
Risk everything - or gain nothing.
Geoffrey de Charney - 1356
Deeds - Not words
Remembering Joe (CrazedWeasel)