What points does this video make, then?
OK, let me do it. The clip refers to the work of Geoffrey Ashe, a Cambridge historian who thinks the Arthur of Geoffrey of Monmouth’s account, although a composite figure, may have been based in part on a historical c.5th Briton warlord called
Riothamus. He also thinks there is evidence that Cadbury Castle in Somerset (in England) may have been the basis for Monmouth’s fictional Camelot.
https://en.wikipedia.org/wiki/Geoffrey_Ashe
In what respects does this back up the claims of your crank protégé? As far as I can see he invents 2 other quite different Arthur prototypes and is preoccupied with making preposterous links to Troy and the lost tribes of Israel, and even invents a catastrophe in the c.6th due to cometary debris. Barking.
(I am mildly interested in that Ashe relies in part on the Breton tradition of Arthur. I am writing this from an island in the Golfe du Morbihan, in Brittany. There’s a lot of Arthurian ballocks round these parts, largely associated with the mythical enchanted Forêt de Brocéliande.
https://en.wikipedia.org/wiki/Brocéliande)