Does the violence and cruelty of Islamic State mirror that of Christianity in Tudor England? Up to a point, according to Peter Kosminsky – at least, there are intriguing parallels.

Kosminsky directed Wolf Hall, the acclaimed BBC adaptation of Hilary Mantel's novel, and the comparison occurred to him during the filming.

Now he's written a four-part drama for Channel 4, The State, which goes behind the barbarities of the radical fundamentalists to look at the real lives of the British jihadis who joined them.

He reflects on the parallels in an interview with Michael Buerk for the Radio Times. In the time of Henry VIII, Christianity was almost the same age as Islam is now. 'It's an intriguing idea 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 and his researchers digested a mountain of information about British jihadis, including interviews with those who had returned. Among the drama's characters, composites made up of several real people, is Shakira (Ony Uhiara) – a doctor with a child who she takes with her to Syria.

Her creed is appalling, but he wants to make the audience care about her. ''We do no service to victims of the blood-drenched cruelty of that regime by pretending those who carried it out are all psychopaths,' he says. '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.'

Islamic State is militarily on its last legs, having lost its Iraq stronghold of Mosul and being about to its Syrian base in Raqqah. However, Muslims still sympathise with its aims, and not just in the Middle East. As Kosminsky says, the trend for British Muslim girls has shifted from trying to find a secular boyfriend of whom their parents would disapprove. Now, 'The super-cool boyfriend is a very pious guy, who prays five times a day and grows his beard. It's a status thing.'

Kosminsky expects to be criticised from both sides.

'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.'