May 31 (UPI) -- Ncuti Gatwa has left the BBC/ Disney + sci-fi series, Doctor Who , after two seasons and former franchise co-star Billie Piper is taking his place as the 16th incarnation of the titular time-traveler. "You know when you get cast, at some point you are going to have to hand back that sonic screwdriver and it is all going to come to an end, but nothing quite prepares you for it," Gatwa said in a statement Saturday. "This journey has been one that I will never forget, and a role