Samantha Willis has one of the hardest journeys in Survivors, starting as a member of the government, and finding herself the leader of a commune over which she has the power of life and death. The Last Enemy and Torchwood guest star Nikki Amuka-Bird dons the power suit and speaks to Paul Simpson.

Is your character the last surviving government minister?

Yes she is. That's one of the most remarkable things about her. She's a junior health minister when you meet her, and she is put in charge of handling the media attention that the epidemic is drawing to it. She's thrust into the spotlight, and she's as shocked, horrified and terrified as everybody else by what's actually going on. However she has to remain composed, make more and more decisions, and take more and more responsibility as other members of the government are going down. She's really out of her depth.

Is she worried about her own family?

Of course. She has to push that aside in a way, which was one of the hardest things when I was reading the script for the first time. She is given no choice. She can't turn her back on what's going on and she can't run away from it. She has to move forward and take that position of being the last contact that the public have with the government.

Do you think she's been tested like this before?

It's fair to say that the day you meet her is the hardest day of her life. She starts off the day thinking it's routine stuff. She doesn't know how serious the epidemic is. She's just reassuring the public that the government have everything under control, and obviously that's not the case. She's having to think in the moment and step up to the plate, which she does brilliantly. Some of the things that drew me to her is that she takes it on rather bravely.

As a member of the government, does your character get any of the blame?

I think the scale of it is so great that no one can really be blamed. It's something that happens so quickly and is so devastating that people are looking forward to how they can survive another day, rather than wondering why it happened.

How much research did you do into what the government would really do?

They didn't share any of their plans with me, even though I tried to get out state secrets! A friend of mine, who's a Labour adviser, took me around the Houses of Parliament where we bumped into an ex-Irish Health Minister who was quite helpful. He talked me through the day to day routine and what might be asked of me. But he drew a blank when I asked what would happen if most of the population was wiped out.

There seems to have been a taste for apocalyptic drama in recent years with the likes of I Am Legend and 28 Days Later. What do you think is feeding the public appetite and do you like them yourself?

I'm a fan of that genre. I've seen all of those. Initially, you want to see what the world is going to look like without its population. You want to see the spectacle of that moment, and that effect.

Survivors takes a slightly different approach. This is much more about life afterwards. It starts at the moment that 28 Days Later stops. It goes right into the human dramas, the human stories, and the new relationships that are formed. In 28 Days Later and I Am Legend, the main characters were very isolated. This is about people reconnecting with each other, starting again and redefining communities.

And, of course, there are no zombies in Survivors...

28 Days Later was popular because the zombies were fast moving and dangerous and edgy. In Survivors, you don't know who to trust. The other Survivors could be dangerous. Everything has now become a luxury, whether it's food, water or shelter, and while you'd expect people to all come together and help each other, that's not exactly how it happens. The whole thing has a thriller quality to it. It's a little bit suspenseful, and you're not sure where it's going.

The threat level has to be heightened in movies due to the shorter running time. Do you think it's easier for TV shows to concentrate more on the characters?

I thought about Lost when I first read Survivors. Lost has a planeload of people with no connections to each other, who have to come together very quickly. In our show, they form alliances, so it could be to do with being afraid of people, or compassion.

As a former minister, does Samantha cling to the idea that society can be rebuilt?

I think it becomes her reason for living. She's lost her family; she's lost everything. If something like that happened to you, you'd think "Why me? Why am I the last one standing? Why am I alive?" Her purpose becomes to be of some use, and to help others. She takes the responsibility of making whatever decisions she can to build the future.

And presumably the decisions she has to make are no longer abstract?

Her thing is that she is the only one who is thinking of the whole. I think people are living hand to mouth and she is trying to make a decision about how we can re-form, restructure ourselves in society. Anything she can do to start that going is what she's going to do

What was the biggest challenge involved in the project?

Doing my political research was quite challenging. Mainly, the challenge was making that imaginative leap. We have to believe it and root it in some sort of reality for the audience to believe it. At the same point, it's a hopeful story, and it's triumphant. It’s about the human spirit prevailing. You're trying to find that balance, where you've got to imagine that you've lost everything but finding the will to live, and what to live for. It's all about getting the balance right.

Survivors is currently airing on Tuesday nights on BBC One.