Jenna-Louise Coleman will replace Karen Gillan as Matt Smith's companion in Doctor Who, it was announced this morning.
The 25-year-old actress, best known for her role as Jasmine Thomas in Emmerdale, will join the BBC sci-fi show in the 2012 Christmas special.
"I'm beyond excited," Coleman said today. "I can't wait to get cracking. Working alongside Matt I know is going to be enormous fun and a huge adventure."
Head writer and executive producer Steven Moffat 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."
Moffat added: "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 Christmas special will be the last of six episodes shown in 2012, with eight more to follow in 2013. Karen Gillan's last appearance as Amy will be in the fifth episode of the new series - an encounter with the Weeping Angels.
"Not everyone gets out alive," Moffat said. "And I mean it this time!" The episode will also mark the last appearance of Arthur Darvill as Rory.
Moffat told RadioTimes.com last night that the new run would focus more on stand-alone episodes than an overall story arc.
Before Doctor Who, Coleman will be seen in all four parts of Julian Fellowes's Titanic. She plays Annie Desmond, a stewardess. The series begins this Sunday on ITV1. She will also appear later this year in Dancing on the Edge, a BBC2 series by Stephen Poliakoff.
Read everything you need to know about Jenna-Louise Coleman here - and tell us whether you think the actress will make a good Doctor Who companion.