Secret is finally out. Peter Capaldi has been revealed as the 12th actor to play Doctor Who on the BBC sci-fi series. Capaldi replaces outgoing star Matt Smith, who has played the lead since 2010. "It's so wonderful not to keep this secret any longer, but it's been so fantastic," 55-year-old Capaldi said. Show producer Steven Moffat announced the news on the live BBC special Doctor Who Live: The Next Doctor Sunday.