In Outcasts, Ashley Walters plays Expeditionary Force leader Jack, while Michael Legge is Tipper, the rebellious genius who helps prevent the settlement on Carpathia avoid destruction. Speaking at the launch of the show, they shared their hopes with Paul Simpson…

What was it about the material that attracted you?

Michael Legge: For me, the script was fantastically written, and Kudos have a fantastic track record. Any actor is going to jump to work for them. When we got out there we only had episodes one and two; it was being written while we were out there essentially, but they were such fantastic episodes. It was all very inventive.

Ashley Walters: I think Ben [Richards] did a really good job. The genre came totally out of the blue for me – I never thought I'd be doing sci-fi at this stage in my career. I was overwhelmed and really glad to be offered the part.

I got the call and was offered the part six days before I went to South Africa, so I didn't have much time to think about it or to prepare. I have family and children here so it was a really hard decision to make solely based on that, but when it came down to the script, the project, the production company and working with the BBC again it was a no-brainer for me.

What do you look for in a script?

Michael: Good writing – you keep reading it. Each character has a different voice, and it’s based in some sort of reality. You can hear the voices and parallel each character to people that you know. It’s a recognition of characters.

Ashley: I suppose it’s like reading a good book in certain ways. You get to read a lot of scripts and you start to realise that not everyone can write. Many are difficult to get through. With Outcasts, it was a no-brainer: you read it, and it was wow! I knew it had never been done before, and it was high concept, but for me, it just felt right. I wanted to play that part, be that guy, and if I feel like that about something then I want to do it – even if there are five other people going for it.

What are your characters looking for?

Ashley: For Jack it’s a new opportunity to get the respect that he thinks he deserves. He spends a lot of time trying to prove his intelligence and understanding about what’s going on around him. He’s looked down on a bit in the beginning by others than Mitchell.

There’s a huge division between the PAS officers and the expeditionaries, which creates loads of conflict. Jack’s problem is that some of his friends are PAS officers as well, but he’s such a determined and forceful character that he will do whatever it takes to get the job done. A lot of time you see him turn on people you think are his friends but it’s for the greater good to uphold what he’s there for, which is to protect the people there.

Jack has a very strong mentality and is physically very strong. He is able to do a lot of things that most humans are not capable of when it comes to strength and his physicality. He is basically a brute.

Michael: Unlike some of the other characters, Tipper has no other choice; he’s been taken away to this planet as a boy, because he’s a child genius; he has a photographic memory and a very high IQ. When he gets to the planet, he wants to rebel against why he’s there, so he doesn’t work for PAS. Because he doesn’t have family and friends around him in transit or on Carpathia, he becomes fiercely independent.

He also has his music, so he sets up a pirate radio station. His objective is just to live in the present and have fun. PAS frequently ask him to help because of his genius, and often he says no. He just wants to run his shack with his decks in. He’s one of the few light characters – he deflects a lot of the darkness in Forthaven.

What part of the process did you particularly enjoy?

Ashley: It’s hard to say, because a lot of it was action-packed and fun. Spending time on those different locations – sand dunes, rocks, cliffs, mountains – was just amazing; there was a variety that you don’t get when you’re here.

It was a great cast. I spent a lot of time working with Eric Mabius because our characters form a relationship. Those things alone for me were exciting.

If things got bad here, would you volunteer for this sort of project?

Michael: No. Horribly, I think it’s potentially a very real happening in the future. I think that’s what’s really interesting about this. It would be terrifying. When I was talking about the darkness, you can imagine the anxiety of going thousands of miles not just from your home, but from your planet, and with such a small amount of people… it must be appalling.

Ashley: The reality is it’s something we probably all would consider, particularly with family and kids, if we couldn’t live on Earth any more.

Were you sci-fi fans?

Ashley: No. But there weren’t a lot of effects on this. Every now and again you had a green screen behind you.

Michael: It didn’t feel like sci-fi!

So how have you described the concept to family and friends?

Ashley: I’ve been saying, “Just watch it.” It gets to a point where it’s impossible to describe. For a lot of my friends, sci-fi isn’t a route they wanted to go down.

Is it the programme that could convert non-sci-fi fans to the genre?

Ashley: I think so. It’s essentially a drama, not about where we are – that’s incidental. It’s about how we’re dealing with it, and how we relate with one another. Everyone will be able to relate with the issues we’re dealing with.

Outcasts concludes on 13 March 2011 (BBC One).