What's the story of 'The Next Doctor'?
"Obviously I have to be a bit of a spoilsport and can't tell you too much, but what I can tell you is the Doctor we know arrives in London in 1851. There he meets the other Doctor, played by David Morrissey, and his companion Rosita. They're basically trying to find out what's going on because there's a few dubious events taking place. As you probably know, the Cybermen make an appearance again, which is great, and we've got a new monster called the Cybershades which you need to look out for. They're all ruled by Miss Hartigan, played by Dervla Kirwan, who's the villainess in the storyline. That's all I can say. You'll have to watch to find out more!"
What are the Cybershades? They look like dogs with cyber-faces.
"They're funny little things, aren't they? They've got robotic faces and they're all covered in feathers. I didn't know what to make of them at first. I thought they were quite nice and thought I might borrow one of their outfits for Friday night! They're quite menacing but they're obviously not as strong or scary as the Cybermen. They pop up quite a lot in the episode - they're always coming out of dark corners and stuff. They're a bit of a nuisance to be honest!"
How would you describe Rosita?
"She's a proper feisty Cockney girl - she gives as good as she gets. She's very much on the good side, she's very loyal and she's got a strong relationship with the other Doctor. She was a lot of fun to play but funnily enough a lot of people have been saying there isn't a lot of difference between her and myself in real life!"
What was she doing before she met the other Doctor?
"Oooh! I'll tell you a secret... we don't want to offend any of the children watching but she was actually a lady of the night! She wasn't up to much good before, so thank goodness the other Doctor came along and gave her something a bit more constructive to do!"
I'm frightened to ask - how did the other Doctor meet her?
"Well, one night she was out earning her living and a Cyberman came to attack her. The other Doctor came to rescue her and it went from there. He wasn't a client, he came and saved her!"
Russell T said that Rosita is 'probably cleverer than the two Doctors put together'...
"Yeah, she is. She's definitely got a very good head on her shoulders. You shouldn't be deceived by her - she does actually get them out of a few tricky situations. She is a big help to them, definitely."
We know she becomes assistant to both Doctors over the course of the episode, but how?
"Yeah, she does. I can't actually say how it happens, but as the episode goes on there's a twist in the storyline, something's revealed and she needs to go off to help the Doctor that we know. She has a bit of both of them... but that not in way!"
"At first the other Doctor's a bit of a threat. The Doctor comes into London and he finds the other Doctor claiming to be him, so obviously he's a bit wary at first. As the episode goes along, they start working together and they find some common ground. They do develop quite a good relationship through the episode."
Does the other Doctor have a TARDIS?
"Yes, he does have a TARDIS. Hahahaha! But I can't tell you how big it is, you'll have to wait and see I'm afraid!"
Were you a fan of Doctor Who before you got this job?
"Funnily enough I wasn't, you know. I've always known that it has a huge following but I didn't realise how many people watched it before I started working on it. I'm not one of these massive fans, but funnily enough I always watch the Christmas special. It's amazing to think Catherine Tate did it, then Kylie did it and then they trusted me enough to take it over. I'm really chuffed - this is more than I could have asked for."
And how was it working with the two Davids?
"Oh, it was horrible, they were awful. They were rude, they came in late... only joking! Honestly, they were really lovely. Obviously it was really daunting at first because it's such a huge show, but as soon as I arrived on set for my first day David Tennant came over and gave me a huge hug to welcome me to the show. David Morrissey was lovely too and came over to say hello. They both kind of took me under their wing and then it was kind of like having two older brothers who were both picking on me! It was like working with two old friends - by the end of the first day I felt like I'd been there for ages, because it's just such a lovely team to work with."
Did you know David Tennant was leaving Who when you filmed the special?
"No, not at all! The first I heard about it was in May when I came back from some filming in Cardiff and everyone was asking me because they thought I would have all this inside information, but I really hadn't! Then it was confirmed later, but it really is a shame because he's been such a huge asset to the show and he's wonderful to work with. I wish him all the best and I'm sure he'll do fantastic in anything else he chooses to do."
How about you and Who? Would you go back again?
"You'll have to wait and see! I'd be lying if I said I didn't want to do it again, because it's such a wonderful job, but it depends on whether my character survives or not."
What have you been doing since filming Who?
"Well, I had a small appearance on Katy Brand's Big Ass Show as a Sugababe! I look quite different from Rosita because I've got a little see-through dress and a peroxide blonde wig on! I used to work with her on Tittybangbang so it was really nice for her to ask me to work on her show. At the moment I'm doing my first pantomime at the Compass Theatre in Ickenham. It's Dick Whittingon's Cat and I play the villain this time, which is a bit of a change for me - but it's a lot of fun being bad!"
Doctor Who airs Christmas Day at 6pm on BBC One.