BBC set to unveil who will replace Matt Smith as the new Doctor Who on Sunday New Doctor Who set to be unveiled during a ground-breaking live episode Their identity is being kept a secret using the codename 'Houdini' Speculation is rife the new Doctor could be a woman for the first time Dame Helen Mirren and comedienne Miranda Hart are both in the running The Thick of It star Peter Capaldi has also been touted for the role It has been two months since he announced he was leaving Doctor Who. And fans of the show will finally find out who will be replacing Matt Smith as the 12th incarnation of the Time Lord this weekend. The new Doctor Who will be revealed live on BBC1 on Sunday in a one-off programme at 7pm. Groundbreaking: Matt Smith's replacement as the new Doctor Who will be unveiled during a one-off live episode of the show on Sunday night Moving on: Smith has played the Doctor for the past three years, but announced he would be stepping down earlier this year It will be the first live unveiling of the reincarnated Doctor and follows endless speculation about who will be next, including the possibility of the first female or black Doctor. Helen Mirren, Olivia Coleman and Miranda Hart, have all been put forward as suggestions, as has Billie Piper, who played one of the Doctor's former side-kicks. The current favourite is The Thick of It star Peter Capaldi, with Ben Daniels of Law and Order and James Bond actor Rory Kinnear also thought to be in the running. However producers have kept the new Doctor's identity a closely-guarded secret, even going to the extent giving him or her the code name "Houdini." First lady: Dame Helen Mirren (left) and Miranda Hart (right) have both been touted as replacements for Smith Joining in with the speculation on the half-hour programme, which is hosted by Zoe Ball, will be a panel of past Doctors as well as Smith, 30, who will leave the show at the end of this year's Christmas special after three years playing the role. Doctor Who is a popular science fiction drama about a time-traveller who moves through the universe in his Tardis time machine with his companion, currently played by Jenna-Louise Coleman. It first aired in 1963, with William Hartnell as the Doctor, but has never featured a woman in the lead role. Favourite: Peter Capaldi, pictured left playing BBC's Mr Nasty Malcolm Tucker is said to be in with a strong chance. Right, the first Doctor, William Hartnell Earlier this year, Steven Moffat, the show's chief writer and executive producer, hinted that the next Doctor could be a woman, having first suggested it as a joke more than a decade ago. Ahead of Sunday's programme Moffat said: "The decision is made and the time has come to reveal who's taking over the TARDIS. For the last of the Time Lords, the clock is striking twelve. BBC drama controller Ben Stephenson added: "We can't wait to unveil the next Doctor with everyone live on BBC1 on Sunday night. Amongst all the speculation and betting, there has been lots of fun and intrigue at work as we've been using the codename Houdini as a decoy. It's the biggest secret in showbiz, even those working with the new Doctor on other projects at the moment have no idea they are in the presence of the 12th incarnation.