43-year-old Marshall is known for his roles in Love Actually, Death at a Funeral, and My Family. Gareth Cattermole / Getty There has been much speculation over who will replace Peter Capaldi when he leaves "Doctor Who" this December after four years on the BBC show.

Now, a "show insider" has told The Mirror Online that the actor who will become the 13th Time Lord will be Kris Marshall.

While it was previously understood that Capaldi's replacement would appear after he retires from the Tardis after the 2017 Christmas special, the source also said that the new Doctor would join the show during the 10th series, which starts tonight.

"Kris Marshall has already joined the cast and will regenerate at the end of this series, not in the Christmas special," the source told The Mirror.

Bookmakers had made bets that "James Bond" star Ben Whishaw would take over the time-hopping drama, according to the Daily Mirror. Other candidates included Richard Ayoade, Rory Kinnear, Miranda Hart, and David Harewood.

However, the Mirror source added: "They won't risk a woman Doctor. They want a David Tennant type."

43-year-old Marshall is known for his roles in Love Actually, Death at a Funeral, and My Family.

Meanwhile, a BBC spokesperson has said that no casting decisions have yet been made for series 11.

Capaldi first took on the role in 2013, replacing Matt Smith, who has gone on to star in Netflix drama "The Crown."