Did you expect the train massacre to come back to haunt Mitchell in series three?
"I knew there'd be repercussions, because it's such a big part of the story. But I didn't know it would be so big! I didn't know at the time, otherwise I probably wouldn't have done it! It's fun though. It's a big story and it's important for Mitchell. It's one of the biggest [storylines] of this series."
Will we see a lighter side to the character after the darkness of series two?
"I don't know. Probably not. It's always up and down with Mitchell. Annie comes back - Mitchell goes and saves her at the beginning of the series, so there's loads of high moments and low moments. But the happy times are mixed with him trying to escape from police and lying to Annie. It ebbs and flows the whole way through. I don't know if it's darker [than last series] but it's a rollercoaster."
Will there be any more flashbacks to Mitchell's past?
"Yeah, we go back to the 1920s. It's fun to do. I just love playing the old Mitchell, because you can forget about everything. You can just play him as this almost Libertine character. He's completely reckless and he can really indulge in the relationship that he has with Herrick. He can look at him differently, without sceptical eyes. He can look at him as a mate and somebody that he's inspired by and maybe aspires to be. I always find [the flashbacks] fun, just to mess around with that relationship. And to play Mitchell before he got really boring! Before he got a conscience!"
Is there any new romance in store for Mitchell?
"He hooks up with Annie in this season. They get together pretty soon after he goes and saves her from Purgatory. That's his relationship this year."
Do you think their relationship will work?
"It has its moments! Any relationship is hard for Mitchell because he's got too much baggage. There's way too much history that he needs to get over and he can't. He's too good at lying and playing games. I don't think you can go into a relationship carrying [those things] because it will always come back. I think any relationship in Mitchell's life, platonic or not, is always doomed."
Is Mitchell jealous of George and Nina's relationship?
"I don't know if it's a jealousy thing. I think he just realises that George can't live on the merits of his best mate for the rest of his life. He needs to settle down, be a normal person and do the things that Mitchell can't really do. George is trying to sort his life out a little bit more and stabilise it slightly. That might mean cutting off certain aspects of his life and changing things dramatically. Mitchell's aware of that."
With the addition of Robson Green and Michael Socha as two new werewolves, is the show focusing more on the wolves than the vampires this year?
"There's definitely a lot of wolves around! We were just shooting a scene where there's five of them in the kitchen. But again, the vampires have their own storyline. It's more interwoven this year. In the last couple of seasons, the vampires very much had their own story. It was a different thread, whereas this year it's intermingled a little bit more."
"I think he's back with the house. He has a premonition that he's going to be killed. That plays the whole way through the series. He's trying to figure out who [his attacker] is and why. On that journey, he meets some new vampires, and some come to meet him, for certain reasons. But there's none of that vampire Alcoholics Anonymous stuff [from the last series]. He's not trying to step into anyone's shoes this year. He's just dealing with his own problems."
How do you feel about the vampire character being named Aidan in Syfy's remake of the show?
"It was a surprise. My friend told me before we went to Comic Con, which was cool, because somebody mentioned it at Comic Con and I don't think I would have believed them had I not known! I guess it's a little weird, but it's also kind of flattering."
Did you have any input into Mitchell's storyline this season?
"No, not at all. The writers have their thing. We're just the actors and we don't have much of a say when it comes to that kind of thing. I think every actor wants a certain amount of control. Maybe not control, as such, but just to be part of the process. But it's not necessary, I guess. We're not writers. I can't sit down and do their job, so maybe it's not fair to [interfere]."
Do you think your performance has altered how Mitchell is written?
"I think a lot, actually. When the episodes for the first season were written, [creator Toby Whithouse] obviously had no idea who was going to play the character. Working on the show, Toby and the producers get to know you and the way you speak. I could see on the second series how it changed. Things just became more fluid and it was easier. It helps to know somebody. This year particularly there are words and little phrases popping up [in the script] that the actors would use and throw around on-set. But it's all good and it comes from an organic place, so I think it helps everybody."
Since Russell, Lenora and Sinead have all appeared in Doctor Who, would you be interested in completing the set?
"I think if I said no, I'd be killed! If only for that reason, I think it'd be fun to do Doctor Who, yeah."
What sort of role would you like to play?
"I've no idea, because I've never seen an episode!"
Being Human returns for a new series on January 23 on BBC Three.
Excited about the show's return? What do you think about Mitchell and Annie's romance? Sound off below!