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
The Lodger (Doctor Who) for Rose Tyler and the TARDIS to catch him up in a few days, and by chance saving the Earth by hiding it from the passing space fleet of a violent alien race. The story was based on ideas that Roberts had since a child to imagine the Doctor experiencing everyday human life and his enjoyment of stories set on Earth rather than in space. Roberts' original comic strip appealed to new executive producer Steven Moffat, who enthused to Roberts that he had "got to do" "The Lodger" as an episode. Roberts had previously had the idea to make the