[Werthead]

Derfel Cadrn is actually in the Arthurian legendarium. He's not as front-and-centre in the legend as Lancelot or Gawain or Merlin, for example, but he is there in most versions of the legend (although he's not quite so constant a figure in more recent interpretations). Also, the first-person viewpoint is essential in these books. I think if BC went to third-person, he'd want to cover everything and would end up with a ten-book series. Using the first-person approach forces him to move quickly and to skip events happening off-screen (other than acknowleding they happen).

I'd say the greatest success in this series was in the character of Guinevere (the most well-executed character-reversal since Jaime Lannister in A Storm of Swords), whilst Lancelot was an excellent inversion of the stereotypical legend. I was disappointed with Nimue's character arc though.