The BBC series Doctor Who has been renewed for a fourth season, the BBC announced at a special preview screening in London this week.

The third season of the new Doctor Who, which will begin airing in the UK on March 31, sees the return of David Tennant as the Doctor but with new companion Martha Jones, played by Freema Agyeman. Agyeman replaces the tenth Doctor’s original sidekick Rose Tyler (Billie Piper). The show’s executive producer Russell T. Davies did not say whether Tennant will return for the fourth season, which is set to air in 2008.

Doctor Who is seen in the United States on the SciFi Channel, which will air season three episodes this summer.

At the preview screening of the first two episodes of season three, it was confirmed that John Simm, who plays time-traveling cop Sam Tyler in the BBC series Life on Mars, will guest-star in the final two episodes of the third season. Simm will play a mysterious politician known as Mr. Saxon.

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It’s been rumored that Simm’s character will be revealed as the Doctor’s old nemesis, the Master.

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Source: Scifi.com