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
Space and Time (Doctor Who) the camera, such as when the Doctor, Amy, and Rory watched the future Amy and Rory enter the TARDIS. "Space" and "Time" were broadcast during the Comic Relief Red Nose Day telethon on 18 March 2011 on BBC One. The telethon was watched by 10.26 million viewers. The BBC posted the episode in two parts on their official YouTube channel. The mini episodes were included as bonus features in the "Complete Sixth Series" DVD and Blu-ray box set, released on 21 November 2011 (Region 2) and 22 November 2011 (Region 1). Lucy Mangan of "The Guardian" responded positively, noting it