How did you get involved with Collateral?
I became involved through director SJ Clarkson, who is an old friend of mine. We met up for lunch while we were both working in LA and she mentioned Sir David Hare, the Collateral script and that she was considering the offer to direct it. She gave me a brief outline of the story and I remember thinking then how exciting it sounded and telling her that she must do it.

She’s an incredibly talented and exciting director and I firmly believed that SJ and David Hare working together on a political thriller would be a match made in heaven. A few months later she called me while I was about to start filming Doctor Who in Cardiff and said that not only had she taken the job, but that she and David would like to offer me the role of the MP, David Mars. I agreed immediately of course, without even reading the script.

When I did eventually read it I was thrilled. It's a wonderful script, it’s certainly the best I’ve read of its kind since Paul Abbott’s State Of Play. And it’s the first opportunity I’ve had to play an MP, which brought a new challenge. I was the journalist in State Of Play, so if any more political thrillers come my way after this it’ll have to be the cop!

So who is David Mars, and how does he fit into the plot?
I think David Mars is essentially a good man. He’s a somewhat frustrated but hard-working member of the shadow cabinet, and even though he despairs at the state of the Labour Party and many of its policies, he’s a loyal constituency MP. He’s not afraid to be outspoken and on more than one occasion he finds himself in hot water with the party leader because of that.

I think he’s a man of principle and loyalty, while at the same time being a little shambolic. His private life is complicated of course - he risks his job by helping out his old friend Jane (Nicola Walker), a local vicar whose lover (who just so happens to be in the country illegally) was the sole witness to the murder. On top of this, David’s ex-wife Karen, with whom he has a daughter, is the last person to see the victim alive. The murder also happens in David’s constituency, so he inevitably gets dragged into the drama.

The relationship between David and Karen was an interesting one to explore; they’re very ill-matched (hence the divorce) and it was an extremely short marriage, but they are forced to interact because of the shared responsibility of their daughter. David’s written some pretty fiery scenes for them which were great fun to shoot.

What drew you to the drama?
I’m a huge fan of David Hare’s work. He’s one of our finest playwrights and I’ve wanted to work with him for many years, so I'm extremely grateful for this opportunity to do so. He’s got a great socio-political mind and his dialogue is razor sharp and beautifully written, so as an actor it’s a joy to perform.

I think bringing political commentary to the small screen is very important and we have a great history of wonderful dramatists in this country, writers and directors who have produced and continue to produce, biting and essential political drama (and satire) for the small screen. This ranges from Alan Bleasdale, Ken Loach and Alan Clarke, to Abi Morgan, Paul Abbott, Tony Marchant, Armando Iannucci and Jimmy McGovern... the list goes on.

It’s an important part of who we are as a nation to be able to comment on the political situation, and in the current climate we need it now more than ever, so the fact that one of our greatest writers has chosen to write a state of the nation political thriller for 2018 can only be a good thing.

How was it working with the rest of the cast?
SJ has assembled a great cast and a great team of incredibly talented people for Collateral, so it was an absolute joy to work on. Everyone worked extremely hard to do justice to David’s script and as ever with SJ (we worked together on Life On Mars) the mood on set was a joyous one, despite the subject matter.

Amazingly, I hadn’t worked with either Billie, Nicola or Carey before, and have always been a great admirer of all their work. They’re all exceptional talents so it was a real thrill for me, a dream job really. I even got the chance to work with my daughter Molly. She plays David and Karen’s daughter Elfie in a few scenes, so that was a wonderful experience.