"It's been four years. It's been the best four years. It's been wonderful, it's been a privilege to work under Steven Moffat. But I think when you gotta go, you gotta go It's sad, I'm going to miss it. I'm going to miss Comic-Con as well. It wasn't an easy decision, but I dunno, you can't play it forever. And, look, they'll get someone amazing and brilliant, and that's the great thing about the show. It continues, and it will get bigger and better. And you'll forget about me."