Ciaran Hinds is perfect as Langton. What’s it like working with him?

He’s one of my main draws to come back every time. He’s a wonderful, kind man and a dear friend. Everyone talks highly of their co-stars but he really is, out of all the people I’ve worked with, up there as the favourite. I feel privileged that I get to play with him. He’s so brilliant.

At the end of the last series you realised he [Langton] is not the man you thought he was. Do you think their relationship will recover?

I don’t know if it will ever recover to the point that it was before but I think that’s life. People we love disappoint us. She had him quite high on a pedestal. He’s not an angel and neither is she. She put Langton in the same category as her father who she completely idolised. What develops now, in this series, is a more realistic relationship. But it’s more complicated than it seems; it’s chemistry.

You’ve just finished filming Flightwith Denzel Washington…

I just finished before Christmas. Robert Zemeckis is the director with Don Cheadle and Denzel and Melissa Leo and John Goodman. It was a wonderful experience. I play a heroin addict; very different to playing an up-and-coming detective.

Do you like that aspect of your job; the fact that every project’s different?

Definitely. The variety is fabulous. It’s always challenging; it’s forever fun. Maybe later I will be more interested in being locked into one television show for ten months of the year, because you’re able to have stability which really has its perks after a while. I feel like a bit of a gypsy in this job. I’m forever flying and staying in hotel rooms and away from home. It’s hard. I loved it in my twenties but now I’m less keen. But variety is the spice of life; it keeps me on my toes. It’s good to be scared. I was really scared going into the Robert Zemeckis movie. It was a big deal for me - my first role in America, playing an American. But they were healthy nerves, it shows that I really care and I think that’s important in any job.

Stylist talks to Kelly Reilly