The eighth series of Doctor Who, otherwise known as Series 8 or Season 34 to avoid confusion with Season 8, is the eighth series of the revived Doctor Who, which began airing in 2005. Steven Moffat continued as head writer and showrunner. The series was the first series to feature Peter Capaldi as the Twelfth Doctor, who succeeded Matt Smith in the 2013 Christmas special, The Fall of the Eleventh. Jenna Coleman also returned as Clara Oswald, who once again served as the Doctor's primary companion, and Sean Biggerstaff would join the cast as well to play Michael Green, who would also act as a companion. John Barrowman and Alex Kingston would also return to the cast to play their respective characters of Captain Jack Harkness and River Song, who would be recurring companions.