Series 4 (Doctor Who 2005)

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Series 4 of Doctor Who started on the 5th April 2008.

David Tennant stayed on as the Tenth Doctor, and Catherine Tate reprised her role as Donna Noble, following her one off in the The Runaway Bride.

This series featured several (former) companions returning; Freema Agyeman, returned as Martha Jones for five episodes of the series, which began with The Sontaran Stratagem following her three episode spell with Torchwood. Jack Harkness crossed over from Torchwood for a second time later in the series. Billie Piper returned as Rose Tyler for a three episode stint starting with Turn Left, all three returned in The Stolen Earth along with Elisabeth Sladen as Sarah Jane Smith. These were further joined by Noel Clarke and Camille Coduri in Journey's End.

Series 4 featured several milestones. It is the 30th ever broadcast season of Doctor Who, and features the 750th broadcast episode, which was The Stolen Earth, the 50th new series episode, The Unicorn and the Wasp, and the 200th broadcast story of Doctor Who, Midnight. The finale episodes The Stolen Earth and Journey's End also took the revived series to new heights of popularity, scoring the highest viewership ratings since the Tom Baker era and according to the media both episodes scored Appreciation Index ratings unprecedented for an ongoing scripted drama series.

As with the preceding three seasons, Series 4 incorporated several ongoing story arcs or background threads which were resolved in the finale episodes. In Series 4 these threads included: Donna Noble's evolution, Rose Tyler's attempts to return to her original world and the Doctor, the disappearance of bees from planet Earth, recurring references to planets and moons disappearing, and the coming of "The Darkness".

Series 4 marked the last full season to be produced by Russell T. Davies, Phil Collinson and Julie Gardner. Collinson left following Journey's End, and Davies and Gardner have announced they will depart following production of a series of specials planned for 2008-2009 in lieu of a regular season. When the show resumes weekly broadcast in 2010, Steven Moffat will be its head writer and show-runner.