List of Doctor Who episodes (1963–1989)  "Doctor Who" ceased production in 1989, then resumed in 2005. The original series (1963–1989), generally consists of multi-episode serials; in the early seasons, and occasionally through its run, serials tend to link together, one story leading directly into the next. The 2005 revival trades the earlier serial format for a run of self-contained episodes, interspersed with occasional multi-part stories and structured into loose story arcs. For the first two seasons of "Doctor Who" and most of the third (1963–1966), each episode carries its own title; the show displays no titles for overarching serials until "The Savages", at which point the episodic titles cease. The titles below, for these early serials, are those in most common circulation, used for commercial releases and in resources such as the "Doctor Who" Reference Guide and the BBC's classic episode guide. With the show's revival in 2005, the programme returned to individual episode titles. Due to the BBC's 1970s junking policy, 97 episodes of "Doctor Who" from the 1960s are no longer known to exist. As a result, 26 serials are currently incomplete, with one or more episodes represented only by audio and, in many cases, clips or still frames. For commercial release, some episodes have been reconstructed using off-air audio recordings, paired to surviving visuals or newly commissioned animation. The story numbers below are not official designations; they are meant as a rough guide to placement in the overall context of the programme. There is some dispute, for instance, about whether to count Season 23's "The Trial of a Time Lord" as one or as four serials, and whether the unfinished serial "Shada" should be included. The numbering scheme in this list reflects an internal practice of describing "Planet of the Dead" (2009) as the 200th story. Other sources, such as the Region 1 classic "Doctor Who" DVD releases, use different numbering schemes, which diverge after the 108th story, "The Horns of Nimon" (1979–1980). The first incarnation of the Doctor was portrayed by William Hartnell. During Hartnell's tenure, the episodes were a mixture of stories set on Earth of the future with extraterrestrial influence, on alien planets, and in historical events without extraterrestrial influence, such as "Marco Polo", one of the lost serials. In his last story, "The Tenth Planet", the Doctor gradually grew weaker to the point of collapsing at the end of the fourth episode, leading to his regeneration.