The Doctor is the title character and protagonist in the long-running BBC science fiction television series Doctor Who. The character has also been featured in two cinema feature films, one made-for-television film, and a vast range of spin-off novels, audio dramas and comic strips connected to the series. In the series, “the Doctor” is the alias assumed by a centuries-old alien who travels through space and time in his TARDIS, frequently with companions. Since the show’s inception in 1963, the character has been portrayed by twelve lead actors. The transition from each succeeding actor is explained within the narrative of the show through the plot device of “regeneration”, a biological function of his race that allows their change of cellular structure and appearance with recovery following a potentially fatal injury. A number of other actors have played the character in stage and audio plays, as well as in various film and television productions. The character’s enduring popularity led The Daily Telegraph to dub him “Britain’s favourite alien”. The incumbent Doctor is the Twelfth Doctor, played by Peter Capaldi, who succeeded Matt Smith in the role in the 2013 Christmas special “The Time of the Doctor”.