Board Thread:What If?/@comment-173.245.80.12-20140903054558/@comment-37001937-20190529225423

''They had no way of explaining how they knew Lancelot was a Shade (or proving that he was) without admitting that they'd used Necromancy, aka magic. ''

Arthur knew that Gaius was a pseudo-follower and student of the old religion and magic. It was under Gaius's purview to tell Arthur that there was more to Lancelot than met the eye. Morgana used necromancy first, and Gaius did it to protect the kingdom. Of course these writers wrote it in a way that Lancelot fails the autenticity test because he doesn't know that Merlin has magic.