The Office star gives the lowdown on swapping a nine-season desk job for prison riots, looting shops and car chases.

Can you describe your character in the show?

Her name is Rhonda and she's a mum and a librarian who finds herself in a peculiar situation. Her son is a computer genius and hacked into the NSA's computers, but Rhonda takes the fall for him so at the beginning of the show she's in jail for this crime that she didn't commit. She thinks it's probably no big deal and that she'll get let out on bail, but the government decides to make an example of her. It's really hard because her husband is sick in hospital and her son's going to be sent away. So there's all that going on, then news of the apocalypse hits and Rhonda is broken out of jail by the world's other greatest computer hacker. So my character is an ordinary woman who faces some difficult moral choices, and she ends up doing some immoral things that she wouldn't normally do. That's what drew me to the project, I get a chance to do things that are out of type for my character, but are actually completely in character due to the circumstances of the show.

Can you relate to Rhonda and the things she does for her son?

I have two kids and I have to say that I would do anything I could to protect them. But more than that, if I was in California and they were in Washington DC and I found out that we all only had one week to live I would do anything it took to get to them. I can completely understand Rhonda's drive to get back to her family before the end of the world.

Has the part been fun to play?

It's been so fun. It's so funny because this is the ten-year anniversary of The Office, which is where I got my start and spent nine seasons sitting behind a desk that I really wanted to get out from behind. But in this, I've looted a store, been in a prison riot and a car chase - I get to do so many fun physical things in different locations. It's been a completely different experience.

And have you enjoyed working so closely with Megan Mullally?

I love working with Megan. We have similar personalities so we've been getting along so well. I love having a female sidekick, it's really exciting to work with a female comedian. And Megan is so much more than that. In Leanne, she's created a character that she's completely lost herself in. When we were shooting the prison scenes, which took three or four days, it wasn't until the end of the last day that the supporting artists realised who she was. When they realised she was Megan Mullally, they freaked out and all wanted to take pictures with her. Everything about her is different, her hair, her look, she's gone totally underground and it's really cool to work with someone with that kind of artistry and commitment. She's also really funny off camera, I love her.

Has the experience of working on a British production been different to your previous jobs?

Yes, completely different, and that was another thing I was looking for, I wanted to get out of the American entertainment system, I wanted to experience something completely new. After The Office wrapped I went to New York and I did a play, and again that was a totally different artistic experience and this has given me that as well. In America, we have so much food on set all the time - so much food everywhere, it's like a Vegas buffet 24 hours a day.

You guys do not do that. It's great, I have not gained any weight during this show! I love that every day at four o'clock a man comes around with a tray of buns and treats and biscuits and everyone has tea, which I thought was from the olden days, but you guys actually do it. You actually have afternoon tea every day - it's adorable.

How would you describe the show?

What I love about it is that it's about the apocalypse, but it doesn't take itself too seriously. The characters are all going through such an emotional experience but are still able to laugh about it. It's quite the British way of dealing with things. Is that what it is? I love it, it's so funny. The show is about an odd assortment of people who are all dealing with a very big extinction-level event, so there's a lot of action and drama. The stakes are high and the stakes are real, but there's a lot of laughter as well.

So if you heard news of an impending apocalypse, how would you spend your final days?

With my family, and that's why I think my character's journey is so relatable to me. I'd also eat as much as I want, too. No more worrying about carbs, it would just be macaroni and cheese every day, please.