answers: three
context: they witness the mysterious Face of Boe (Struan Rodger) prophecy to the Doctor that "you are not alone." They are rejoined by former companion Captain Jack Harkness (John Barrowman) in a three-episode adventure where presumed-deceased archenemy and fellow Time Lord the Master (John Simm) becomes Prime Minister of the United Kingdom and enslaves the Doctor for one year. Martha's plan sees the Doctor infused with the world's psychic energies, and he easily defeats the Master, who seemingly refuses to regenerate and dies in the Doctor's arms. Following this adventure, in the dénouement of series finale "Last of the Time Lords", </s> a lone Doctor composing his musical "Ode to the Universe" before being interrupted by the small alien Graske (Jimmy Vee). In lieu of a 2009 series, Tennant appears as the Tenth Doctor, without a regular companion, in several special episodes over the course of 2008 and 2009, the last of which aired on New Year's Day, 2010. In the Christmas special "The Next Doctor", the Doctor mistakenly believes he has met a later incarnation of himself in an amnesiac Londoner (David Morrissey), with whom he saves Victorian-era London. "Planet of the Dead" (Easter 2009) features jewel thief Lady Christina de </s> Patrick Troughton Patrick George Troughton (, 25 March 1920 – 28 March 1987) was an English actor. Classically trained, he played the second incarnation of the Doctor in the long-running British science-fiction television series "Doctor Who", which he played from 1966 to 1969; he reprised the role in 1973, 1983 and 1985. He appeared in several fantasy, science fiction and horror films. Troughton was born on 25 March 1920 in Mill Hill, Middlesex, England, to Alec George Troughton (1887–1953), a solicitor, and Dorothy Evelyn Offord (1886–1979), who married in 1914 in Edmonton. Patrick had an elder brother, Alec Robert (1915–1994),
question: how many seasons did david tennant play doctor who