There was a television programme last week that I caught most of, accidentally, at someone's house and this was all about tracing the myth and history of Arthur (Arthur Stone is pronounced Ar Thur Stone, incidentally, just as Ar Thur Dent). I've got much better ones than this at the Knar. But anyway
The conclusion of this programme was that Arthur was a real person who died in a battle near to the Roman Wall, at a place called Camboglana. I've not looked it up on the map - it was a fort possibly. A country gentleman took the cameras into a typical Northumbrian open-sided shed and it was packed with Roman carved stones. Michael Wood scraped some of the moss off them and looked for images of Arthur among the carved figures.
The King's Crag and the Queen's Crags are named after Arthur and Gwenifir - I think this is from Tomlinson's Guide To Northumberland.