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
Companion (Doctor Who) focus on the character of Rose Tyler and characters connected to her. For example, although Adam Mitchell was a companion by the standard definition, he appeared in only two episodes and was arguably a less significant part of the 2005 series than Rose's sometime boyfriend Mickey Smith, who was not technically a companion but appeared in five episodes (or six, including a brief appearance as a child in "Father's Day"). Mickey later gained full-fledged companion status when he travelled in the TARDIS in the 2006 episode "School Reunion". In that episode, Sarah Jane Smith referred to Rose as the Doctor's