::: The ODNB entry for him is interesting, and definitely seems to imply that there isn't a lot known about him that can be said with any certainty. It is probably best to check out the sources used for the qualifiers - and make them clearer. What is probably meant is "If he existed in the manner that the chronicles relate" much like how Arthur is considered - no one really doubts that there is someone who inspired the stories of Arthur, but it is highly unlikely that he lived anything like what was even ascribed to him in the earliest accounts, much less later ones.    -