Rumor is Naomi Watts has been cast in the Game of Thrones prequel series. No idea who Naomi is playing and there are no plot details available. The only thing we know is they want British actors for all of the roles or actors with a perfect British accent. The pilot is set to shoot early next year so we should be getting some cast announcements soon.
Also, been hearing that Triss will indeed be in a few episodes of the first season of The Witcher and they may have already cast someone. Someone British.
Apparently British accents are a requirement for all fantasy television shows.