That’s where GRRM’s clues seem to be pointing that way, as a number of fans have been commenting on the web and Twitter. David Bradley, presently best known for his role as Argus Filch in the Harry Potter films, fits the clues to a tee. Born in 1942, the actor was part of Laurence Olivier’s National Theatre (hence the Olivier name check), played Cohen the Barbarian in one of the Pratchett adaptions (Cohen being a parody of Conan the Barbarian, presently being played by Jason Momoa, aka Khal Drogo), was in Nicholas Nickleby (Dickens), Vanity Fair (Thackeray), and been in an adaption of The Canterbury Tales (Chaucer).
It’s an interesting choice, in that the actor is about twenty years younger than Lord Walder is in A Game of Thrones, but his acting credentials can’t be denied, including a 1991 Olivier Award for his portrayal of the Fool in King Lear with the Royal National Theatre. Below is a clip featuring him in a similar role, as Henry VIII’s fool, Will Somers, in The Tudors:
As an extra note, in the comments to his post, GRRM notes that Castle Black’s one-armed blacksmith, Donal Noye, is not appearing (at least not in the first season). I’ve heard that Tyrion Lannister will be getting much of his role in the first novel (don’t worry, he’s not losing an arm!)