The Doctor (Doctor Who) Time Lords a fixed number of twelve regenerations, meaning that every Time Lord had a total of thirteen incarnations including the original. The plot of "The Time of the Doctor" involves the Doctor receiving a new cycle of regenerations from the Time Lords before his expected demise, triggering the regeneration into the Twelfth Doctor, played by Peter Capaldi. The origins of the programme were explored in the docudrama "An Adventure in Space and Time" as part of the 50th anniversary celebrations of "Doctor Who", which starred David Bradley as William Hartnell. Although Time Lords resemble humans, their physiology differs in
Doctor Who (film) Peter Capaldi. Eccleston and Capaldi would go on to play the Ninth and Twelfth incarnations of the Doctor, respectively, in the revived series of "Doctor Who" which began in 2005. Eccleston turned down the offer to audition for the TV Movie because at the time he felt he was not yet an established enough actor and did not want to be associated with a "brand name" so early in his career. Capaldi declined because he felt it was unlikely that he would be given the part. Of those actors who originally auditioned for the role of the Doctor, a number