Jenna-louise Coleman has been announced as the new 'Doctor Who' companion and is ''funny and clever and exactly mad enough'' to join the show.

The 25-year-old actress beat hundreds of hopefuls to be named the Doctor's new assistant in the BBC One sci-fi series and executive producer Steven Moffat knew he had found the right co-star for Matt Smith when she first auditioned.

Speaking at a press conference to unveil Jenna-Louise as the series' newest star today (21.03.12), the showrunner said: ''It always seems impossible when you start casting these parts, but when we saw Matt and Jenna together, we knew we had our girl. She's funny and clever and exactly mad enough to step on board the TARDIS.

''It's not often the Doctor meets someone who can talk even faster than he does, but it's about to happen. Jenna is going to lead him his merriest dance yet. And that's all you're getting for now. Who she's playing, how the Doctor meets her, and even where he finds her are all part of one of the biggest mysteries the Time Lord ever encounters. Even by the Doctor's standards, this isn't your usual boy meets girl.''

The actress - who has previously appeared in 'Emmerdale' and superhero movie 'Captain America: The First Avenger'- will become the Time Lord's assistant in the 2012 Christmas special and she can't wait to start work on the exciting role.

She said: ''I'm beyond excited, I can't wait to get cracking; working alongside Matt I know is going to be enormous fun and a huge adventure.''

It has also been revealed current companions Karen Gillan (Amy Pond) and Arthur Darvill (Rory Williams) will leave the series in a battle with monsters the Weeping Angels which has fatal consequences.

It will be the episode before Jenna-Louise makes her debut.

Steven explained: ''Amy and Rory will leave in a final encounter with the Weeping Angels in episode five. Not everyone gets out alive and I mean it this time.''

He has also confirmed the Doctor's most famous foes the Daleks will be returning for a new storyline.

'Doctor Who' Series 7 will be split across 2012 and 2012 with six episodes airing this year and eight being broadcast in 2013.

The adventures are being branded blockbuster movie-style episodes which will lead up to the show's 50th anniversary in November 2013.