Doctor Who is a television series.
Doctor Who . The transition from one actor to another is written into the plot of the show with the concept of regeneration into a new incarnation -- an idea introduced in 1966 to allow the show to continue after the departure of original lead William Hartnell who was becoming very ill at the time . Peter Dougan Capaldi ( born 14 April 1958 ) is a Scottish actor , writer and director , best known for playing the twelfth incarnation of the Doctor in the television series Doctor Who . In the long running British science fiction television series Doctor Who , regeneration is a biological ability exhibited by the Time Lords , a race of fictional humanoids originating on the planet Gallifrey .