Could the British prisoner on Demonreach be King Arthur?

We know the prisoners on Demonreach are very powerful. In Skin Game, he says he’s “someone who needs to be here”, indicating both that he has done something monstrous and considers himself monstrous because of it.

King Arthur’s greatest crime was one that’s less well known in Arthurian legends: that he had tons of children, babies, fruitlessly killed. After Merlin told him that a child born on May Day would destroy Arthur (unknown to Arthur at the time, it was his incest-born son, Mordred), Arthur then rounded up all the newborn noble children born around that day, put them on a ship, and had it sunk, killing them all. It would make a lot of sense if it’s the thing Arthur regrets most in his life, especially since it didn’t kill Mordred, who still went on to destroy Arthur and Camelot, and so he killed the children for nothing.

(I will admit that a large part of my theory here has been influenced by Guy Gavriel Kay’s Fionavar Tapestry, which uses that part of Arthurian legend to great, excellent effect.)

I’m sure also that in the Dresdenverse, Arthur may not have been the saint the stories make him out to be; who knows why he might deserve to be held on Demonreach? Maybe we’ll find out. 

King Arthur’s death story also has him, mortally wounded, being borne away on a boat in a lake to a mysterious island where he won’t die. Like, to an island where he’ll be kept...in stasis.

We will eventually need a wielder for Excalibur Amoracchius. Maybe he’ll help Thomas to wield it? Maybe Harry will release him for the BAT?

Just throwing the thought out there.