Christina de Souza

Planet Of The Dead
She was arrested at the end of the Planet of the Dead But the Doctor released her

Behind the Scenes
Actress Michelle Ryan was reportedly considered for the role of Martha Jones after the departure of Billie Piper from the series in 2006. The announcement of her casting has led to UK media speculation that the character of Christina may continue as the companion of the Eleventh Doctor in 2010, however as of March 2009 her only announced appearance is in Planet of the Dead as a "one-off" companion, with a different one-off companion appearing in the special that follows. If she is destined to become a full-time companion, this will become known during the second half of 2009 as production begins on Series 5.