After months of speculation, the relatively unknown 26 year old actor Matt Smith will become the eleventh and youngest Time Lord in the BBC’s long running science fiction TV series Doctor Who, taking over from David Tennant.

Matt Smith is best known for playing the lead role of Danny in the BBC2 series Party Animals, set in the world of young politicians.

"I'm flabbergasted,” said the new Doctor. “I haven't slept really! [Doctor Who] is an iconic part of our culture, and now I'm taking that on. It's nerve wracking. Exciting. Exciting.

"It's an iconic part of our culture, my grandad knows about it, my dad knows about it, it's been going since 1963 it has the iconic status of Robin Hood or Sherlock Holmes."

Matt Smith seems an unlikely choice to play a long lived Time Lord. The character needs gravity, depth and experience, and while I know little about him, he appears way too young.Considering the Doctor’s companions are usually 10 or 20 years younger, does this mean we’ll be seeing 16 or 6 year olds in the TARDIS in Doctor Who's sixth season? The BBC may be aiming for a younger audience, but I think they've taken it too far. David Tennant seemed too flippant and inexperienced to me and he was 37.

"The Doctor is a very special part,” said Steven Moffat, who takes over from Russel T. Davies as Executive Producer of the series. “It takes a very special actor to play him. You need to be old and young at the same time, a boffin and an action hero, a cheeky schoolboy and the wise old man of the universe.

"As soon as Matt walked through the door, and blew us away with a bold and brand new take on the Time Lord, we knew we had our man.

"2010 is a long time away but rest assured the 11th Doctor is coming – and the universe has never been so safe.”

Previous actors rumoured to have been considered for the role included Chiwitel Ejiofor (the villain in Serenity), Patterson Joseph, James Nesbitt, Sean Pertwee (whose father Jon played the role in the 1970s), James McAvoy, John Simm (who played the Master in the series) and David Morrissey (who played a character called the Doctor in last year's Christmas special The Next Doctor).

David Tennant, who took over from Christopher Eccleston in 2005, will now complete four hour-long specials (Doctor Who’s fifth season) and then presumably undergo the regeneration sequence that will see him transform into Matt Smith.

Updated! Matt Smith talks about being cast as the new Doctor on You Tube. The clip is from the BBC's Doctor Who Confidential.