Peter Kosminsky on his new jihadi drama The State: “We have to confront the fact that terrible things are done by people who are not inherently evil”

Islamic State makes the Khmer Rouge look like the Salvation Army. It wants to re-create the seventh century with Kalashnikovs and rocketlaunchers; to kill or enslave all those it regards as infidels; and to bring on the Apocalypse, when Jesus will come back to earth with a spear to kill the devil and bring about the end of days.

It’s a death cult, but around 1,000 Britons have gone to extraordinary lengths to join it.

Kosminsky was finishing off Wolf Hall, the adaptation of Hilary Mantel’s novels about Tudor England, when he conceived the idea of a drama about what happened to IS’s British recruits. There are striking parallels, he says. In the time of Henry VIII, Christianity was almost the same age as Islam is now. “It’s an intriguing idea,” he says, “that we were inflicting brutal public punishments, hanging, drawing and quartering people in the streets, putting heads on spikes, burning people alive over, what seem to us now, minor doctrinal differences.”

Kosminsky is a precise man, careful not to push this too far – Christian cruelty was “mainstream”, he says, IS an “unrepresentative sect” – and he is mortified when he unwittingly describes the comparison as “ultimately wrongheaded”.

Kosminsky and his researchers spent 18 months building a picture of what life was like for the British jihadis. They trawled the online blogs and worked their way through the court documents of those who have been prosecuted. They talked in detail with returning jihadis, though he is reticent over who, how and where.

The main characters are composites. Shakira (Ony Uhiara) is a doctor, like half a dozen or more Britons who have gone to Syria. She’s a single mum and takes her child with her, as many British jihadi women have done. Jalal (Sam Otto) is following his brother, an IS “martyr”, also a common story.

Kosminsky makes them engaging and human, knowing that’s a risk. “It’s the biggest challenge I’ve ever faced as a dramatist,” he says. “How to engage the audience’s sympathies with characters who are inherently unsympathetic, and make you care what happens to them.”

And Kosminsky believes we should care. “We do no service to victims of the blood-drenched cruelty of that regime by pretending those who carried it out are all psychopaths. It might give us comfort to think ordinary people can’t descend to that level of vileness but history proves that’s rubbish. We have to confront the fact that terrible things are done by people who are not inherently evil.”

My problem with The State, as with the real thing, is why? Kosminsky doesn’t even try to answer the question. Shakira is a doctor, almost by definition intelligent and caring, a strong, capable woman who, as he says, “won’t take s**t from anyone”. Yet she goes to enormous lengths to join Dark Ages fanatics committed to mass murder, slavery and routine crucifixion; a regime that subjugates women (we see them savagely beaten for showing more than their eyes in public). And she takes her nine-year-old son with her.

I find myself shouting at the screen: “What the hell do you think you’re doing?”

To be fair, Kosminsky’s dealt with radicalisation before, in his drama Britz (Channel 4, 2007). He’s probably right that his new series would get bogged down with flashbacks if he tried to explore his characters’ motivation. But he’s candid enough to say if he did so we might not bother about what happens to them, and that, to my mind, is more problematic.

Their story is a journey from euphoria to disillusion through a landscape of savagery. It begins with camaraderie: a band of brothers for Jalal; for Shakira a cloistered sisterhood who see themselves as “lionesses among the lions”.

“They all talk of the relief of finally being with like-minded people,” Kosminsky says. “Of safety and strength in numbers. Of leading a pious life without needing to make excuses. Doing something morally pure.”

That does not survive reality. Jalal’s perverted idealism eventually can’t cope with the pitiless barbarism all around him (a struggle played out on Sam Otto’s impassive face in a performance of extraordinary subtlety). Shakira kicks against the stifling world in which she’s trapped herself.

“As a dramatist,” Kosminsky says, “I was interested in head versus heart. For whatever reason, they have made an intellectual commitment to IS, but what happens when that collides with the reality of life and death in the ‘Caliphate’? In my experience, in any contest between the brain and gut, the gut wins.”

How true that is, is difficult to tell, as he admits. British jihadis tended to be put in the front line while more experienced Iraqis and others are held back. “The attrition rate is above 70 per cent,” he says. “Most who appeared on those videos are dead.” And who knows what those who have returned to the UK really think?

Islamic State is crumbling, the city of Raqqah, where the drama is set, has been bombed to oblivion. Militarily, the “Caliphate” may soon be history.

But though the overwhelming majority of Muslims have no truck with IS, a disturbing number, here and elsewhere in the West, have told pollsters they sympathise with its aims. And not just Muslims. One in four French people aged between 18 and 24 had a favourable, or very favourable, opinion of IS when they were polled by ICM in 2014.

The trend among British Muslim girls had been to find a boyfriend their parents disapproved of. “Now, that’s completely changed,” says Kosminsky. “The super-cool boyfriend is a very pious guy, who prays five times a day and grows his beard. It’s a status thing.”

That doesn’t mean the boyfriend will become a jihadi or that she will be radicalised, but it is a sign that religion is increasingly important to those in the extremists’ target group.

Two things are predictable about The State. It will swiftly be labelled as “controversial”. All Kosminsky’s work is. “There will be Muslims who complain: ‘Here we are, terrorists again’,” he says. “Others will see it as a wilful attempt to make people who take this path more sympathetic than they should be. I just want people to get a more complex view of an incredibly sad and emotive subject. Their ideas about IS won’t change, but their view of those who get involved might be more nuanced.”

I’m sure it will also be showered with awards, like his previous dramas. By then, he will have moved on – a film about Mozart for the BBC, then a sequel to Wolf Hall.

At 61, this quiet and meticulous film-maker, a former BBC trainee who was sacked after his first six weeks as a script editor for being “completely useless”, has produced his most powerful piece of work. It’s almost unbearable to watch, but it would be unforgivable to miss.

Interview by Michael Buerk

The State is on Sunday 20 – Wednesday 23 August at 10pm on Channel 4