Doctor Who: The Thick Of It star Peter Capaldi is revealed as the twelfth Time Lord

Will appear on screen in 2014 following eleventh Doctor Matt Smith's departure in this year's Christmas special
BAFTA winning actor will join existing Doctor's Assistant Jenna Coleman
At 55, he is the oldest actor to play the Time Lord since the First Doctor William Hartnell in 1963
Previously guest-starred in a 2008 episode of Doctor Who

PUBLISHED: 19:30, 4 August 2013 | UPDATED: 20:35, 4 August 2013

Peter Capaldi has been revealed as the twelfth Doctor Who.

The 55-year-old actor, best known for playing Malcolm Tucker in The Thick Of It, was announced as the new Time Lord in Sunday's live BBC TV special.

The Scot's appointment comes two months after Matt Smith announced he was quitting following four years as the time-traveller.

The Twelfth Doctor: Peter Capaldi is revealed as the new Time Lord

Peter, a lifelong Doctor Who fan who won an Oscar for Live Action Short Film in 2005, admitted he found keeping his new job a secret from his daughter Cecily difficult.

He said: 'It's so wonderful not to keep this secret any longer.

'For a while I couldn't tell my daughter. She was reading the rumours on the internet and getting upset that they weren't mentioning me. I kept saying "Rise above it, rise above it."'

Best job on television: The Thick Of It actor posed for his first Doctor Who portrait on Sunday morning, taken by Rankin

Peter admitted he used to play Doctor Who as a child growing up in Glasgow, and was thrilled he was able to play it as an adult.

He enthused: 'I'm a lifelong Doctor Who fan. I haven't played it since I was nine. As an adult actor I've never worked on it.

'(For the audition) I downloaded some old scripts from the internet and pracitised that in front of the mirror.'

Big secret: Peter admitted it was difficult hiding his big new role from family and friends

Speaking about the casting of Peter, executive producer and head writer Stephen Moffat said: 'We got the 12th person around and made a home video of him being the Doctor and showed it to the relevant people, and everyone said "Yes, that's the Doctor."'

Moffat continued: 'It's an incendiary combination: one of the most talented actors of his generation is about to play the best part on television. Peter Capaldi is in the TARDIS!'

As fans of the show will know Peter has previously appeared in small roles in an episode of Doctor Who and its spin-off Torchwood.

He plays a character called Caecilius in a 2008 episode entitled The Fires of Pompeii, and the role of John Frobisher in 2009 episode of Torchwood entitled Children of Earth.

Sayonara: Departing Doctor Matt Smith gave some words of advice to Peter

Sunday's live reveal episode was shown simultaneously on BBC America so UK and US viewers found out his identity as the same time.

The 35 minute show, entitled Doctor Who Live: The Next Doctor, was hosted by Zoe Ball.

Matt, who joined the show in 2010, will appears in his last scenes in the Christmas Special, with the 12th Doctor appearing in 2014, joining current assistant Jenna Coleman, who plays Clara.

She said in a statement: 'I'm so excited Peter Capaldi is the man taking on the challenge of becoming the Twelfth Doctor.

Can't stand the tension! Zoe Ball announced Peter as the new Doctor in a TV special

Congratulations! Show guest Liza Tarbuck gives Peter an affectionate grab

'With Steven's writing and his talent I know we'll be making an amazing show with an incredible incarnation of number 12. I can't wait to start this new adventure!'

Reflecting on his Time as the Doctor, Matt said: 'I'll miss playing a character who can bounce from A-Z and be the smartest in the room and the silliest in the room... what a character!

'Of course there's a part of me that doesn't want to go. There are no parts like this.'

Comedy star: Peter won a BAFTA and British Comedy Award for his portrayal of Malcolm Tucker in The Thick Of It

Speaking about his successor, Matt remarked: 'I just want to wish my successor all the best and just say good luck and good on your for getting it.

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He's a huge fan of the show and a really nice guy. The casting made me really excited. It's a really canny choice. Good luck man. It's gonna be a thrill.'

Among the guests on the live show were the Fifth Doctor Peter Davidson and Bernard Cribbins, who played Wilfred Mott.

The latest actor to be cast in the role comes as the show plans to mark its 50th anniversary with a special episode.

The anniversary episode on November 23 - exactly 50 years after the first episode was broadcast - will feature Matt and Jenna, as well as stars of previous series David Tennant, Billie Piper and John Hurt.