The Black Guardian Trilogy

Doctor Who is a British science fiction television programme produced by the BBC. As of 1 July 2017,^[update] 839 episodes of Doctor Who have aired, concluding the tenth series. This includes one television movie and multiple specials, and encompasses 275 stories over 36 seasons. Additionally, four charity specials and two animated serials have also been aired. The programme's high episode count has resulted in Doctor Who holding the world record for the highest number of episodes of a science-fiction programme. In June 2017, it was announced that due to the terms of a deal between BBC Worldwide and SMG Pictures in China, the company has first right of refusal on the purchase for the Chinese market of future series of the programme until and including Series 15.

Doctor Who ceased airing in 1989 and began again in 2005. Each story in the original series (1963–1989) is a multi-episode serial, with two exceptions: the 1965 cutaway episode "Mission to the Unknown", and the 20th anniversary story The Five Doctors. During the early seasons of the programme, and occasionally through its run, most serials were linked together; usually one story would lead directly into the next. Starting with the 2005 revival, the production team abandoned the traditional serial format for a largely self-contained episodic format with occasional multi-part stories and loose story arcs.

Due to the BBC's 1970s junking policy, 97 episodes from the 1960s are missing, with the result that 26 serials are incomplete, although all of these still exist as audio recordings, and some have been reconstructed. In the first two seasons and most of the third, each episode of a serial had an individual title; no serial had an overall on-screen title until The Savages. The serial titles given below are the most common title for the serials as a whole, used in sources such as the Doctor Who Reference Guide and the BBC's classic episode guide, and are generally those used for commercial release. The practice of individually titled episodes resurfaced with the show's 2005 revival, when Doctor Who's serial nature was abandoned in favour of an episodic format.

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