History is always up for re-evaluation as new facts and knowledge become available. Recently Arthurian studies have undergone a revolution as to the historical Arthur. Until the late 20th century Arthur was regarded as a historical character but in the early 21st century this status is debated. First we must distinguish between the legend, what English students call Romance, and the potential history leaving us with a choice of Arthur being a character from Folklore, a historical character as authentic as Henry VIII, or something else even more complicated.
In order to do look at this accurately, we must therefore ignore the work of Geoffrey of Monmouth and the French tradition of Chretien de Troyes, that introduces staple characters such as Lancelot, and focus on Welsh and British sources.
When did Arthur first appear
Arthur first appears in the Annales Cambriae and the Historic Brittonum, and is portrayed as a leader in post-Roman Britain who fights the Anglo-Saxons. His name also appears in the Y Gododdin again fighting this time in defence of the Kingdom of Gododdin. (Again we must strip away the mythological elements inherent in Welsh poetry that portray Arthur as a defender of Britain against various supernatural threats.) This Arthur is a man who defeats the Saxons at Badon Hill. The location of this seems to be the Roman city of Aqua Sulis, now called Bath. Arthur then goes over seas to establish his own empire.
Facts and figures
Historically we certainly see a warrior leader in the 5th century who fights against the Saxons who wins a great battle, or mounts a defence, stopping the expansion of the Saxons for a generation. We see in the archaeology settlements being abandoned and resettlement in Saxony. We see a determined resistance and organised resistance to the Saxons in the form of refortified Roman Forts such as Lunt Roman Fort in Warwickshire. But was this Arthur? Or was it in fact an amalgamation of leaders from the post-Roman period? Could the Romano-British, known as the Combrogi, unite under what the Saxons called a “Bretwalda” (ruler of Britain)? This seems unlikely, the Combrogi fragmented into Kingdoms such as Cornwall, Powys etc. At the same time we see other characters from the historical record who do the same things as Arthur. Men such as Ambroisius Aurelianus and Lucius Artorius Castus as well as Welsh and British kings such as Riothamus who allied with the Gallic Romans against the Visigoths. If we combine the achievements of Ambroisus, Lucius and the adventure of Riothamus we get the achievements of the documented Arthur. It is certainly possible that such great leaders would go into folklore and be remembered fondly, amalgamated not just as a man but a hero like the Bronze Age Kings of the Greek Dark Age.
Conclusion
It is a reluctant conclusion that there was no historical Arthur but that there was a number of great warriors and leaders during the 5th and 6th century who resisted the Saxons and supported the ailing Roman Empire. The argument seems robust and convincing but I for one declare Artorius Rex quondam, Rexque futures! (Arthur, Once and Future King!)