Fair note: I know Paul Wood slightly. Not exactly friends, but we have crossed paths. Enough to trust his due diligence on a story, at least.
An "Islamic caliphate" has been declared in the Middle East and the group behind it, Isis, has now rebranded itself simply "the Islamic State". Panorama has spoken to a defector about life inside the feared jihadist group.
Isis is not an organisation it is easy to leave. We met a man who had - and he was terrified of the consequences. "The brutality of Isis terrifies everyone," he said. "My family, my cousins, my siblings are all still there. I fear for them. If they can't reach me, they will reach my family."
He was nervous, agreeing to record an interview only after several hours of discussion, over customary tiny glasses of scalding hot, sweet tea. He would talk to us only if we would not reveal his identity. He wrapped himself in a keffiyeh for our camera and we promised not to use his name.
He summed up the jihadists' tactics like this: "If you're against me, then you'll be killed. If you're with me, you work with me. You submit to my will and obey me, under my power in all matters."
There are few accounts of how Isis works. That is no surprise when Isis says it will detain as spies any foreign journalists who enter its territory. So we travelled to Turkey's border with Syria to meet the defector.
The border is a hinterland of safe houses and supply lines for the rebels in the Syrian uprising. Turkey has made clear that Isis is no longer welcome here, so it is possible to meet people who have sought refuge from the Islamic State.
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Paul Wood presents Isis: Terror in Iraq on 14 July at 20:30 BST.
Then available in the UK on the BBC iPlayer
The defector had initially joined an Islamist brigade of the Free Syrian Army to fight the Assad regime. He joined Isis when his whole tribe pledged allegiance to the group - and because he believed in creating an Islamic state.
His first orders, as an Isis fighter, were to attend a course on Sharia, or Islamic law. "Not the principles of Islam, the principles of the Islamic State. So they teach you the Islam they want," he said.
"It appeals to the heart and not to the mind, so that your heart becomes impassioned with their words. This is the first stage. The second stage is military exercises, military training."
Read more: http://www.bbc.co.uk/news/world-middle-east-28269596