The actress told The Guardian “I'm so excited to be working on Doctor Who as it’s such a big and important part of British culture. I can't wait to meet the cast and crew and start filming, especially as we'll be shooting not too far from my home town.”
Showrunner was quick to respond to inquiring questions about the role Williams would be playing against the Doctor with, “It’s not possible to say too much about who or what she’s playing, but she is going to challenge the Doctor in very unexpected ways. This time he might just be out of his depth, and we know Maisie is going to give him exactly the right sort of hell.”
Maisie's character of Arya on "Game of Thrones" is noted for doing that very thing on the show. The actress has filled the demands of the role beautifully and has turned into an A-List star.