The fourth series of Doctor Who, starring David Tennant as the Timelord, is currently showing on BBC One, Saturday nights.
Catherine Tate is reprising her role as Donna the runaway bride from 2006's Christmas special, while Billie Piper is also appearing once again as Rose Tyler in selected episodes. Freema Agyeman, who played Martha Jones the Doctor's assistant throughout the critically acclaimed third series, has also returned to the show to join The Doctor and Donna.