James Graham was an undergraduate at Hull University when he became fascinated by daily press reports of the trial of a respectable home counties couple accused of cheating their way to the top prize in ITV’s Who Wants To Be a Millionaire? At the time, Millionaire was one of the biggest shows on TV, achieving audiences of more than 8 million; at its peak, an incredible 19 million tuned into the programme.

“I couldn’t believe the audacity of the crime,” recalls Graham, his eyes brightening at the memory. “The idea that someone would try to pull off a bank heist in front of the cameras, in front of a TV audience, to steal £1m was just incredible. Like everyone else in the country, I thought they definitely did it.”

Suffice to say, Major Charles Ingram (aka the Coughing Major, as the tabloids dubbed him) and his wife, Diana (sitting in the Millionaire audience, she and a family friend apparently alerted Ingram to the correct answers by coughing discretely), were found guilty and given suspended prison sentences.

Spool forward to 2015. The stage career of the insanely prolific Graham has taken off. Thanks partly to This House, set in the Commons during the turbulent 1970s, when Labour struggled to govern, Graham has emerged as one of the most talked-about dramatists in the country. (This House would subsequently be voted the play of the decade.)

He is given a book by theatre producer William Village, Bad Show: The Quiz, the Cough, the Millionaire Major, written by investigative journalists Bob Woffinden and James Plaskett, which casts doubt on the Ingrams’ guilt. “The proposition of the book is that the story is not what we think it is,” explains Graham. “It’s much more complicated than that. Diving into the book, it was thrilling to have my preconceptions disrupted and altered with new evidence that I’d never even considered.”

Graham is inspired to write the stage play Quiz, based on Woffinden and Plaskett’s book. The play is a huge success, nominated for an Olivier Award, and eventually transfers from Chichester to the West End, in the course of which he adds new material.

Next month, Graham’s three-part adaptation of Quiz, directed by the celebrated Stephen Frears, will be shown on ITV. It stars Matthew Macfadyen as Ingram, Michael Sheen as Millionaire presenter Chris Tarrant, Sian Clifford as Diana Ingram, and Mark Bonnar as Paul Smith, Chair of Celador Television, Millionaire’s producer.

“I had a bit of imposter syndrome  when I first walked into Stephen Frears’s living room,” admits Graham, who looks younger than his 37 years. He is sitting in the London offices of Left Bank Pictures – Quiz’s producer – and, in his dressed-down way, could easily pass for a postgraduate student.

The idea of Graham suffering from imposter syndrome is truly baffling but it does speak volumes about his humility. His many other triumphs include RTS-award winner Coalition, the story of the machinations that led to the Cameron-Clegg Government in 2010, and, of course, Brexit: The Uncivil War, in which Benedict Cumberbatch plays a deeply troubled Dominic Cummings, then largely unknown outside the Westminster bubble.

He continues: “I was nervous at first because Stephen is such a screen legend and I know he is critically astute. I thought: he’s going to think I am a complete fraud; he’s going to know way more about film-making, politics and culture than I do. But he was so generous about what I was trying to do.

“He asked very precise questions. He’s not one of these directors who gives prescriptive or inhibitive notes that limit you. He would ask questions that opened up possibilities.”

The idea of turning Quiz into a TV series came from Left Bank co-founder and CEO Andy Harries. “He came to see the stage show and instantly wanted to do it,” remembers Graham.

"It’s really exciting both to return to a story I was obsessed with as a younger man"

Getting Frears on board was something of a coup. He’d worked with Harries on the Oscar-winning film The Queen, starring Helen Mirren. Quiz is Frears’s first TV series since the award-winning A Very English Scandal featuring Hugh Grant as Liberal leader Jeremy Thorpe.

How involved was the director in Graham’s scripts? “Very involved,” he replies. “I’d only written one of the scripts when I first met him.

“When he read, that he instantly asked where the other scripts were. I told him I hadn’t written them yet, but I was trying very hard. He fed his thoughts into the first script, which had a knock-on effect on how I wrote the other episodes.”

It will be for the critics to judge how the TV series stands in relation to the stage versions of Quiz. What is clear is that Graham has jettisoned a lot of the original material from the versions shown in the theatre, including their potted history of British TV game shows.

In another departure from what audiences saw in the theatre, Graham has given roles to some of the TV executives mentioned in the play. Two of the key people who helped nurture Who Wants To Be a Millionaire?, ITV’s director of programmes, David Liddiment, and his entertainment commissioner, Claudia Rosencrantz, both appear in the series – played by Risteárd Cooper and Aisling Bea respectively.

What, then, attracted him to the story of an apparent crime committed on a TV game show? The subject matter seems far removed from the world of Westminster and Whitehall, where Graham so often sets his stories. Is there a connection between this and his other work, other than him having written it?

“I would still say that it’s political. I think everything is political, even if it doesn’t feature politicians and the corridors of power,” he says. “I was surprised when I felt so attracted to the idea of this story, but I think it was because it tapped into the anxiety that I was feeling at the time – and that we all currently feel – about truth and reality, and the threats to that in the post-Brexit, post-Trump, internet/social-media world, where nothing feels quite trustworthy or stable any more.

“Here is a story about an alleged crime, where there are many different interpretations about how [the Ingrams] did it [and, indeed,] whether they did it.

“It was born out of the age when television, news and media were changing radically. Whether it was the advent of the 24-hour news cycle, the emergence of social media, or reality TV blending drama with truth and fact with faction, I think it comes from the origins of what we’re dealing with today.”

He adds: “It’s really exciting both to return to a story I was obsessed with as a younger man, and to be given another institution – because I love institutions, whether it’s newspapers or Parliament or a referendum campaign – and for, in this case, television to be a vessel to explore all the nervousness I was feeling about truth.”

Quiz shares with his other writing the empathy and even-handedness towards his characters that is a defining characteristic of his work, perhaps the defining characteristic.

Graham has described the story that inspired Quiz as “the most British story in the history of the world”. Quizzes, particularly pub quizzes, are quintessentially British and, as Paul Smith likes to say, they feed into two defining national obsessions – drinking and always wanting to be right.

“I almost think that the most radical thing we could be doing at the moment is creating work that is empathetic and tolerant of different views and dissent"

Is Quiz also a very British story because the British are – or perhaps were – famous for their sense of fair play? “That’s exactly what it is and it answers why we became utterly transfixed by this story 15 years ago – and why I hope an audience will be transfixed by it today. It tapped into something innately British about our sense of injustice when people don’t play by the rules. We are the nation of queuing, who invented cricket with its rules of fair play and good sportsmanship.

“But there is a less attractive side, the tabloid press and its impact on the justice system; its joy in building people up and seeing them come crashing down again. That’s part of tabloid culture, whether it’s Meghan Markle or anyone else.”

So, not so very far from Ink, Graham’s story of how Rupert Murdoch turned The Sun into Britain’s biggest tabloid, or Brexit: The Uncivil War and how both sides of the referendum campaign manipulated truth for their own ends.

In our polarised political culture, it is heartening that someone like Graham might help to calm things down by trying, in his dramatised versions of recent events, to understand people whose views are diametrically opposed.

“I almost think that the most radical thing we could be doing at the moment is creating work that is empathetic and tolerant of different views and dissent,” he says. “I hope Quiz is a warm-hearted, charming version of that. It’s not the Brexit movie at all. It’s not going to divide people in a similar way, but it does pose a question: are they innocent or are they guilty? Does our justice system work or are there flaws in it?

“Are we, as citizens, culpable for sometimes being whipped up as a mob in judging people by our emotions, rather than our brains? I think it does present big questions but, ultimately, in an entertaining story.”

Given the abuse Graham received for Brexit: The Uncivil War, does he ever regret portraying Cummings as a sympathetic, if maverick, figure?

“There’s a difference between being sympathetic and antipathetic. With Brexit, I was never going to please everybody. I didn’t think that I wouldn’t please anyone, but I knew I wouldn’t please everyone.

“As a writer, I don’t know how else to do it, how else to bring people to life, [how else] to get inside their head, to get under their skin, to try to understand what makes them tick.

“I have a – possibly flawed, possibly naive – theory that everyone thinks that what they’re doing is right and good, and we just happen to disagree with them. I think there is a small subsection of people in this world who are selfish and look out for themselves, but I don’t think that’s most people.

“Even though, for example, I voted remain and thought that Brexit would be a bad thing for our country, what would be the point in simply allowing my prejudices to cover up my writing?

“It was a great privilege to actually go inside the head of someone who disagreed with me. I have to believe that Dominic Cummings thinks that Brexit will be a good thing for his country, his family and the people he loves.

“Reasonable people can disagree with that, but there is no point in ­simply presenting people as two-­dimensional villains. It’s lazy writing, dramatically inert and politically unenticing. I don’t know how else to write, other than to imagine that what people think is positive and good.”