An open letter on the casting of Angel Coulby:
glass_icarus has written a really great open letter to the fandom on the casting Angel Coulby in Merlin, the implications of having a black Guinevere and the problems inherant to favouring making Arthur/Merlin canon bound up in that.
It's a really well articulated, thought-provoking piece of writing, and a lot of the comments on it are also very interesting, so I'd reccomend anyone who wants to learn more about this particularly tricky topic both in our fandom and honestly in fandom and the media in general, should take a look.