Image copyright Channel 4 Image caption The Accident begins with a celebration - but things quickly turn sour

Jack Thorne is probably one of the UK's most in-demand writers.

The Bafta winner's CV includes TV series This is England, Skins, The Fades and the forthcoming BBC adaptation of Phillip Pullman's His Dark Materials.

On the West End stage he had a huge hit with Harry Potter and the Cursed Child. And on the big screen, his credits include the Julia Roberts film Wonder plus The Aeronauts, in cinemas in November.

But his latest Channel 4 offering, The Accident, is possibly his darkest work yet.

The four-part drama stars Sarah Lancashire, who also had the lead role in Thorne's 2018 adoption drama Kiri.

The Accident centres around a small Welsh community torn apart when an explosion at a building site causes a factory block to collapse with a group of teenagers trapped inside.

The long-held bonds between families and friends are thrown wide open as an inevitable blame game begins.

While the storyline is fictional, the real life tragedy of the 2017 Grenfell Tower fire, which killed 72 people, looms large in the background.

Image copyright Channel 4 Image caption The community is tight but there is also a sense of isolation

Thorne explains that the plan for The Accident "was always to look at class and restorative justice" but Grenfell shifted his focus.

"I had an idea in my head and then Grenfell happened and the idea changed.

"And the concept of looking at corporate manslaughter and the way a corporate manslaughter trial might work came about."

Thorne reveals he felt unable to take on the Grenfell story itself.

"I was actually offered Grenfell three times by three different production companies… but I didn't feel like there were the facts in place to look at it properly without hurting an awful lot of people, trampling over people's lives.

"It's not to say that there isn't a beautiful drama to be made. I just didn't feel capable of it myself."

But he didn't want to leave it there.

Image copyright Channel 4 Image caption An act of rebellion - a group of teenagers break into the building site

"It felt like TV could tell a story, which was not looking at Grenfell directly, but by looking at another story around that, maybe we could do a bit of light shining."

The first person he looked to for his central character was Happy Valley star Lancashire; in fact, the part of Polly was written with her in mind.

"Sarah's the most extraordinary actress. She is just phenomenal, she makes [rubbish] lines good," says Thorne.

Polly is married to a local politician who championed the construction project that's at the centre of the tragedy.

It's left to her to try to hold the community together and begin the search for the truth.

Lancashire says: "I think with most things that Jack writes there's something that's fearless, he deliberately shines a light on a really difficult case where the public, political and private collide.

"And then he does this extraordinary thing, he takes a huge story and makes it tiny. He does exactly the opposite of what most people do. And then he distils it further and examines it forensically through the eyes of those who are most affected. It's extraordinary."

Image copyright Channel 4 Image caption Genevieve Barr is still best known for playing Amelia in the BBC award-winning series The Silence

Polly's husband Iwan is played by Welsh actor Mark Lewis Jones, who, incidentally, says Sarah "nailed" the Welsh accent.

We won't reveal too much but there is a genuinely shocking scene in the first episode between Polly and Iwan; you could hear a sharp intake of collective breath reverberate around the screening room as it played out.

Jones says: "Iwan looks like a man who is hiding some secrets. That scene was shocking and comes out of nowhere.

"He's a gift to play. He's very complex and damaged. There's a lot of layers there. But the relationship between the two was amazing to explore.

"It's a very distorted strange love story between them.

"And they've known each other for a long time. We both felt that this was a relationship that started when they were kids. And they've grown up together. And at some point, this relationship has gone pear-shaped."

Lancashire says: "Those scenes are challenging but that's the best place to be. Mark is a phenomenal actor so I feel very, very privileged to have had this experience with him."

Image copyright EPA Image caption Thorne says he wants much better representation for people with disabilities on screen

Another key role in the drama is played by deaf actor Genevieve Barr. She plays the part of Debbie, a good friend of Polly whose husband is in charge of security on the fateful building site.

Thorne says getting better representation for actors with disabilities on screen is "my obsession".

"Genevieve was Bafta-nominated about 10 years ago for The Silence and she's barely been on telly since. And she's an incredible actress," he says. "I've worked with her three times and she's brilliant.

"The fact that she's not being treasured and pushed up and made into a star is a frustration."

He believes the entertainment industry is doing "incredibly badly" when it comes to disability and inclusion.

"There's change happening, it's just a disappointment that when we're talking about diversity, disability gets left out of those conversations."

'People need justice'

It's clear by the end of the first episode that there are dozens of questions unanswered, gaps of knowledge that may never be filled.

Thorpe says: "I'm a writer that poses questions, not gives answers. I don't feel capable of doing that. I hope that by the end, there's a sense of a thesis.

"But it's not an easy thing. And the idea that you can single someone out to blame is very, very tricky. But at the same time, it's also very clear that the judicial system hasn't found a way to find the answers.

"People do need justice. And justice leads to things improving. The fact that not all the Grenfell cladding has been taken down is really, really crucial, because it means that the companies that put the cladding up are not frightened enough to remove it.

"And that means that justice is failing."

The first episode of The Accident airs on Channel 4 on 24 October at 21:00 BST.

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