The crowd had done a runner. Apart from Abu Din, who was wagging an admonishing finger at the black van.

He was still wagging it when Albert Pierrepoint got out of the van. And then another Albert Pierrepoint. The faces of the two kindly uncles scanned the street. At the top of the screen I could see the young uniformed copper on his belly, radioing for assistance. Another kindly uncle sat at the wheel of the transit van, gunning the engine.

‘Albert Pierrepoint masks,’ I said. ‘Nice touch.’

‘And the duct tape over the registration plates is an even nicer touch,’ Whitestone said. ‘Whoever they are, they know exactly what they’re doing.’

Abu Din’s bodyguards were nowhere to be seen as the preacher was bundled into the back of the black van without ceremony. It began to reverse at speed down the suburban street and then it was gone, the street gradually filling with worshippers watching it leave, the uniformed copper slowly getting to his feet.

Billy hit a few buttons and the big screen became the standard CCTV grid of nine, all of them views of fast-flowing evening traffic.

‘The CCTV followed them on the North Circular heading in an anti-clockwise direction and then we lost them. And then we picked them up again.’

The grid was replaced by a single still image of the transit van burning on what looked like the surface of an abandoned planet. In the background I could see the faded sign of a giant oil company.

‘They switched vehicles,’ I said.

‘Disabled the cameras in this abandoned petrol station and torched their old ride,’ Edie said. ‘So we’ve got one CCTV camera for every person in London but it does us no good at all because we don’t know what we’re looking for.’

Telephones suddenly began to ring, chime and vibrate. Edie scanned a text on her mobile.

‘Getting the first pictures from what we believe to be the execution of Abu Din,’ she said. ‘Let me put it on the big screen.’

She pounded her keyboard and a hangman’s noose appeared on the TV. The camera zoomed in and then out again, as if getting focused. It settled on the noose, hanging stark against the familiar cell-like space, mildewed with the ages, beyond all light. Then the camera slowly pulled back and you could see the four black-coated figures.

‘Production values definitely improving,’ Edie muttered.

But this time was different. Because there was no condemned man wild-eyed with terror at the centre of it all. Instead the camera focused on a series of photographs on the wall.

Servicemen. Six of them. Smiling, happy, proud.

Edie looked up from her laptop.

‘Getting reports – unconfirmed – that those are the Sangin Six.’