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 Early Adventures portrayed the role of original Barbara actress Jacqueline Hill in the 2013 drama "An Adventure in Space and Time", and Dan Starkey as the Sontarans. The second story also features actor James Joyce in the role of a new companion, Jospa. <section begin=series3 /><section end=series3 /> Frazer Hines, Anneke Wills, Elliot Chapman and Wendy Padbury reprise their roles as the Doctor's companions, with Frazer Hines also playing the Second Doctor. Other characters are also played by Anjella Mackintosh, Wanda Opalinska, Kristina Buikaite, Alistair Petrie, Debbie Chazen, Matilda Ziegler, David Sibley, Kerry Gooderson, Ewan Bailey, Alan Blyton, Judith Roddy, Adam Newington,