I’ve always wondered how much of King Arthur’s story is historically true. I’ve been studying it since I was a boy, and my conclusion is: probably most of it.
Like, for instance, that bit about the sword in the stone.
Alas, I had no idea where to publish my research, and who was going to publish Arthurian research by some guy in New Jersey whose only claim to fame was some short stories in Mike Shayne’s Mystery Magazine? So of course someone beat me to it.
But that only shows that the theory I came up with was both sensible and even obvious–if you knew where to look.