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The Tenth Doctor is the tenth incarnation of the protagonist of the long-running BBC television science-fiction series Doctor Who. He is played by David Tennant, who appears in three series, as well as eight specials. As with previous incarnations of the Doctor, the character has also appeared in other Doctor Who multimedia.
In the series' narrative, the Doctor is a centuries-old Time Lord alien from the planet Gallifrey who travels in time in his TARDIS, frequently with companions. When the Doctor is critically injured, he can regenerate his body; in doing so, his physical appearance and personality change. Tennant portrays the tenth such incarnation. This incarnation's companions have included working class shop assistant Rose Tyler (Billie Piper), medical student Martha Jones (Freema Agyeman) and fiery temp worker Donna Noble (Catherine Tate); he eventually parts ways with them all by the end of the 2008 series finale, "Journey's End", after which he attempted to travel alone for the duration of the 2008-10 specials.
Executive producer Russell T Davies revived Doctor Who after a sixteen year absence with the successful premiere of "Rose", in 2005. Following the BBC's announcement of a second series being commissioned, the story broke that Christopher Eccleston, who played the titular Ninth Doctor, would not be returning for the second series. On 16 April 2005, the BBC announced that David Tennant had been selected for the role of the Tenth Doctor. His first appearance in the series was for 20 seconds following the Ninth Doctor's regeneration at the end of "The Parting of the Ways". His first full episode as the Doctor, barring an appearance in a "mini-episode" during the 2005 Children in Need show, was the 2005 Christmas Special, "The Christmas Invasion". He then appeared in the 2006 series, the second seasonal episode, the 2007 series, the third Christmas special, and the 2008 series. Rather than a traditional series run, 2009 features a series of five specials and a series of animated shorts, all starring Tennant as the Tenth Doctor; he also guest-starred in a two-episode serial of The Sarah Jane Adventures spin-off in that year. Tennant also appears in two animated serials; The Infinite Quest is counted with the third series, and Dreamland is counted amongst the 2008-10 specials. The 'Tenth Doctor era', in this article, refers to the period of Doctor Who in which David Tennant held the role of the Doctor. It is largely the same as the "Russell T Davies era" of Doctor Who, but excludes Christopher Eccleston stories, and places more emphasis on events within the show as opposed to those behind the scenes.
Lindy A. Orthia notes, in the Journal of Commonwealth Literature, that the Tenth Doctor's "companions... are themselves drawn from a cosmopolitan vision"; despite almost all being from London, the Doctor's companions do not represent a homogeneous group. Rather, "all the Doctor’s companions are black, queer and/or working class", putting forward that "Jack, Martha and Mickey all stand in contrast to the original series companions, who were definitely all white and none of whom were openly queer." Unlike the working class companions of the classic series, "none were unskilled workers nor chronically under- or unemployed like Rose, Donna and Jackie." Within the show, the cosmopolitanism ("Multi-raciality, in combination with heightened consciousness about gender and sexual diversity") of Doctor Who, as a world embodied by the Tenth Doctor's companions, "must be defended against the threat of the enemy Cybermen, who wish to make everyone the same by removing “sex and class and colour and creed". The colour-blind multi-raciality of the Tenth Doctor era extends to Earth's past, which is represented "as a place of happy and benign diversity. Depression-era New York contains mixed-race shanty towns led by a black man, while black women populate the streets and royal courts of Victorian England and Enlightenment France" and "The 1920s, 1940s and 1950s are populated with gay men." This gains specific relevance to the companions when the Doctor assures Martha, in 1599 England in "The Shakespeare Code", that she will not be carted off as a slave; the Doctor points out to her the sheer number of black men and women walking the streets of Elizabethan England, as well as men dressed as women. However, Orthia writes, "The Doctor’s colour-blindness extends to referring to Mickey as "Mickey the idiot", irrespective of the elitist hierarchies of "smart white doctor versus stupid black estate dweller." In fact, "The Doctor's battle against evil is perpetual precisely because, like other liberals, he does not recognize the structural oppression that is everywhere around him."