She's flitted between stage and screen for decades, but now Imelda Staunton has her sights set firmly on the latter. She tells Gemma Dunn why, in the current climate, she's keen to branch out.

Imelda Staunton is questioning the ever-growing popularity of true crime.

Be it a documentary series like Making A Murderer, hit drama Killing Eve or the award-winning Serial podcast, there's no denying, as a nation, we're obsessed. And that goes for the Oscar-nominated actress too.

Staunton, 63, says she enjoys watching the genre, then asks, perplexed: "But what is it? Do we want to solve things?

"Why do we want to look at the bad things that go on? Because we're not near it? It's safe in our sitting room? Or does it help us understand it?"

And she queries: "I don't know what it says about human beings.

"Maybe we've got too much time on our hands? Maybe we should be out doing something more meaningful, than just watching people kill each other?"

Maybe. But it's a trend that's sure to pique an interest in her brand-new ITV drama, A Confession.

Penned by acclaimed screenwriter Jeff Pope, it tells the true story of how Detective Superintendent Steve Fulcher (portrayed by Martin Freeman) deliberately breached police protocol to snare suspect killer - local taxi driver Christopher Halliwell (Joe Absolom). A decision that ultimately cost him his career and reputation.

Set in Wiltshire, the six-part series details the case of 22-year-old Sian O'Callaghan, whose 2011 disappearance triggered a missing person's inquiry - led by Fulcher.

Meanwhile, Karen Edwards (played by Staunton), the mother of 20-year-old Becky Godden - who disappeared in 2003, is watching the investigation unfold and soon becomes gripped by fear that her daughter's vanishing is somehow connected.

Despite the story gaining traction in the news, however, Staunton confesses landing the scripts was the first she'd heard of it.

"I'm ashamed to say I didn't know, at first, it was a true story," she declares. "What I found extraordinary were the amount of coincidences, so when I re-read the scripts a second time, it was even more shocking."

She follows: "It is an important story to tell. It's about the families who suffered these terrible tragedies but it's also crucial to cover the police officer's point of view and what happened to the senior officer in charge, Steve Fulcher. It covers a lot of bases."

Did the fact it's based on a real-life event add a certain pressure to the role?

"It does, whether you like it or not," she accepts. "If you'd just written that script you'd think, 'Oh that's great', but yes, the back of my head is absolutely whirring. You feel slightly more responsible somehow.

"I don't know how that manifests itself, but you want to make sure that you honour who's gone before and who's still around."

That includes Edwards, who Staunton admits she was initially reluctant to meet.

"We had about a five-hour meeting and she was terribly nice and forthcoming and welcoming," she recalls, confessing she was also averse to the bereft mother watching her act out the more harrowing scenes on set.

"I didn't ask her any prying questions, I was never going to say, 'How does it feel?' ever, because I think we know it doesn't get any worse than that," details the Harry Potter star.

"I just wanted to get a feel of her - I'm not doing an impression," she reasons. "But just an essence or realising the energy that she has and that all her fuel is driven by grief and rage. She's a real force."

Next Staunton - who began her career in repertory theatre in the 1970s - will star alongside her husband Jim Carter, Dame Maggie Smith and Hugh Bonneville, in the hotly anticipated Downton Abbey film.

"It was great because I got to do stuff with Maggie [Smith] and Penelope [Wilton]," the Rada alumni says of Julian Fellowes' epic. "[Our characters] have a little attitude, which is so nice to do. But people aren't interested in seeing me and Geraldine James - they want the whole gang back on the screen!

"I can't tell because I am a sort of outsider, but you just want it to go down well and it not to be a bloody huge disappointment."

After the emotional toll of A Confession - "There were no easy scenes" - did she long for something lighter?

"Not particularly," Stanton muses. "I was grateful for it because having done quite a long stretch of theatre, with quite a lot of heavy stuff, I thought, 'I'll never get parts ever, on film, like I get in theatre. I just won't.'

"But last year I did a bit on Downton Abbey and then [filmmaker] Romola Garai sent me a script about two years ago... and it was a horror film!" she yelps. "So I'm doing a little bit in that.

"Downton, a bit of horror, I'm shaking it up a bit. I'm trying to be brave enough - because I don't want to do any theatre for a while - to go, 'Right. If you're going to do some film and telly, don't just do the next job that comes along'.

"Hopefully we're in a good climate at the moment, the ladies in the television programmes, ladies that aren't 20. So it's not a bad time!

"But there's no point just saying, 'I want to do a part'," she adds. "Someone's got to write it - and I don't write!"

Staunton won't rule out working alongside Carter and their 25-year-old actress daughter Bessie (last seen in ITV's Beecham House), either.

"The three of us, that would be hilarious!" she says, smiling ear to ear. "We were all in Cranford, which was something that we did years ago. But oh no, I'd love that.

"But maybe [Bessie] needs to tread her own path," she ponders. "Give her a few years and I'll be begging her to work: 'Please let me be in something that you're in'," she mimics.

Now back to her own career path, Staunton concludes: "You just have to be patient and wait for something that will hopefully be interesting - like Romola's film.

"I have no idea what it will be like, I don't know if I understand it, but I loved doing the horror thing!

"I suppose I've almost outstayed my welcome in the theatre because I just went on and on and on," she finishes. "So it's quite good now to just let someone else do the schlepping."

A Confession airs on ITV on Monday, September 2.