Another guest star has been revealed and it is former Primeval star Ben Miller. Ben Miller will be guest starring in the epiosde written by Mark Gatiss. Here is what Steven Moffat had to say about his guest star.
“Mark Gatiss has written us a storming villain for his new episode, and with Capaldi in the TARDIS, we knew we needed somebody special to send everybody behind the sofa. And quite frankly, it's about time Ben Miller was in Doctor Who!”
Ben Miller who is a fan of Doctor Who is ecstatic about being in Doctor Who as is evident from his quote about being cast.
"As a committed Whovian I cannot believe my luck in joining the Twelfth Doctor for one of his inaugural adventures. My only worry is that they'll make me leave the set when I'm not filming."
Doctor Who is filming now and will air sometime this fall on BBC One and stars Peter Capaldi and Jenna Coleman.
Source: BBC Media Centre