(Kiri starts on Wednesday January 10 on Channel 4)

Your new drama is Kiri – could you explain a little bit about the show and who you play?

I play Miriam. She’s a rather colourful character. She’s a social worker. She’s somewhat mischievous. She likes to unsettle people with her directness and earthiness. But she’s also brilliantly flawed, as are most of the best characters to play. She’s really striving to do good in an imperfect world, whilst carrying her own demons, which is very much part of the human condition. It’s what makes these characters live and breathe. She has a defiance, a very strong purpose, a need to do good in society. But she also works very instinctively, she uses her intuition, but in this instance it leads to a catastrophic end.

Can you explain a little bit about where we find Miriam at the beginning of the story?

She makes a decision to allow one of the youngsters that she’s in charge of, Kiri, to visit her paternal grandparents, unchaperoned. It’s a decision taken with all parties’ agreement, and borne out of the fact that her adoption is pending. All things considered, Miriam feels it is a safe situation. But it quickly becomes clear that this decision has devastating consequences, the effects of which are explored in in the series.

The series explores a harrowing and difficult subject matter – does that attract you to a project, or make you more cautious about it?

To be honest, neither. I can tell very early on, reading a script, within six or seven pages, whether I’m looking at real people, and whether I can see and hear real people. Very often it’s not the subject matter that’s the draw, but how it’s dealt with. 

So what was it that attracted you to Kiri?

Well, without a doubt it was one of the best scripts I’ve read in a very long time. I think Jack Thorne is an exceptional writer. This piece is very real, and very raw, and it was also colourful and edgy. It just had a heartbeat. It was leaping off the page, to be honest. I suppose those are the pieces that I’m drawn to, those are the pieces that I want to do, really, because I can do something with them. 

Had you worked with Jack Thorne before?

No. In fact, I think we met, briefly, many, many, many years ago, but we’d never worked together. But of course I was aware of his work, because he’s up there with the best. You kind of always hope that something of his work will come your way, and it did. I was very fortunate in that sense. 

It looks like a fairly thankless task, being a social worker. Did playing Miriam give you a real appreciation of the work they do?

I think, really, it doesn’t take a great deal of imagination to know that anybody who’s working in that public sector finds it a thankless task. And Miriam finds herself, in this story, in the eye of a storm. Anyone who has to be accountable in a time when resources are shrinking, where transparency is necessary, where the pressures are greater, is going to find that it takes a toll. Kiri is a very exciting drama, but it’s also a terrific thing to explore these other areas, because they are very under-explored worlds, to be honest.

Did you do much research?

I spoke briefly to Jack about it, because his mother worked in the caring professions. But there’s very little that one can do, in terms of research, in this instance, because it’s such an individual piece. 

Kiri is all set around Gloucester Road in Bristol, isn’t it?

Yes, it is. We filmed all of the exteriors and stuff there. It’s Miriam’s patch. It’s fantastic, vibrant, really colourful, really edgy, completely non-conformist, which is very much who she is. They sort of complement one another. To be honest, I didn’t know Gloucester Road in Bristol, I hadn’t heard of it, but one of my sons is very familiar with it, because he was at university there. 

Was it an exciting place to film?

Yeah, it was great. I always love discovering places that I know nothing about, it’s one of the perks of the job, and it was a really good place to film. 

How did you get on with the Bristolian accent? Do things like that come quite easily to you?

I spoke to the director [Euros Lyn] about it, and asked him whether he wanted a Bristolian accent. We just decided that it lent itself to the piece. I have to work at stuff, always have to work at stuff. I wouldn’t say I’m naturally gifted in that area. So I had a few weeks at home on my own, just bedding the accent in.

Much of your work over the years has been extremely intense, not least this and Happy Valley. Are you good at switching off at the end of the day’s filming? Or do you carry it with you?

Well, you can’t switch off at the end of the day’s filming, because there’s work to do. We don’t do nine-to-five jobs. You do long days filming, and then you go back and start preparing for tomorrow or the rest of the week. Doing pieces like this is very demanding, you have to learn in the evenings. If you’re leading a piece, the night time is just work time. So there’s no opportunity to switch off.

You are someone whose success has seems to have increased as you’ve got older – in contrast to an awful lot of women in your profession. Is that a sign that there are more decent roles for women out there, or should we not read too much into that?

I wouldn’t read too much into it, to be honest. I think it’s about the choices that you make. I don’t tend to make easy choices. That’s because I have to do work that I care about. I’m not terribly good at being around work I don’t care about!

It will be on Channel 4 from Wednesday January 10, 2018 at 9pm.