The Llamas give us a pretty good roundup of what is known about the historical King Arthur. Or course, being colonials they seem to have a gap in their reference library, to whit A.H Burne’s “Battlefields of Britain”. In this they would have seen that Mount Badon was actually Badbury, on the Marlborough Downs just south of Swindon. Not too much of a surprise actually, as it is on the Ridgeway. Also:

The paramount king of Britain was Ambrosius Aurelianus, “The Last of the Romans”, but he was now an old man and he had long before deputed the command of all the troops in the field to his nephew Arthur.

Otherwise their round up is top notch.