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 – The Ultimate Adventure Doctor Who – The Ultimate Adventure Doctor Who – The Ultimate Adventure was a 1989 stage play written by Terrance Dicks, based on the long-running British science fiction television series "Doctor Who". The play was staged at twenty theatres around Britain, commencing 23 March 1989. It initially starred Jon Pertwee (who had played the Third Doctor in the series) as the Doctor. On 29 April Pertwee was ill, so understudy David Banks, who portrayed the Cyber Leader in the series from "Earthshock" onwards, played the Doctor for the matinee and evening performances. Pertwee continued in the role until 3 June