Doctor Who (series 4) Astrid Peth, who died during the events of the episode. The companions in the regular series had all been in the lead companion role previously: the primary role of Donna Noble, who was introduced in "The Runaway Bride", was played by Catherine Tate for all thirteen episodes. Her return was announced by the BBC on 3 July 2007. Freema Agyeman, who portrayed the Doctor's companion Martha Jones in series three, returned for "The Sontaran Stratagem", "The Poison Sky", "The Doctor's Daughter", "The Stolen Earth" and "Journey's End". Billie Piper, who played Rose Tyler from the first episode of the new
Time War (Doctor Who) to Jack Harkness in "Utopia" that his resurrection by Rose was part of the final act of the War. Following what was for all intents and purposes the removal of the Time Lords, the Doctor believed himself to be the last of his race. The removal of the Time Lords also had a profound impact on time travel. In the 2006 episode "Rise of the Cybermen" when the Tenth Doctor, Rose Tyler and Mickey Smith are trapped in an alternative reality, the Doctor explains that, when the Time Lords were around, travel between parallel universes was less difficult but, with