‘I just hope this operation goes as smoothly,’ said Willoughby-Brown.

The driver of Charlie Two was a middle-aged man in a tweed jacket, horn-rimmed spectacles and a flat cap. The middle-aged woman next to him could easily have been his wife. She had dyed blonde hair and was sitting with a blue plastic handbag in her lap. Anyone looking at them would assume they were a married couple out for a Saturday shop, but in fact they were two of MI5’s most experienced followers.

‘Charlie Two, we’re outside the exit now,’ said the woman.

‘Roger that, Charlie Two,’ said Aspden. ‘If they’ve swapped vehicles they’ll be out in the next few minutes.’

The driver parked opposite the exit but they were on double yellow lines and he knew they wouldn’t be able to stay there for long.

Half a dozen cars came out and joined the traffic. A police car was heading their way. ‘We’re going to have to either move or identify ourselves,’ said the woman in the passenger seat.

‘I see them,’ said the driver.

‘Give it a few seconds, then move on,’ said the woman. ‘We mustn’t show out whatever happens.’

As the driver stared at the barriers holding back the two lines of traffic leaving the centre, he saw two Asian men sitting in front of a blue Ford Transit. He didn’t recognise the driver but he knew the man in the passenger seat. It was one of the tangoes. ‘Charlie Two, I have eyeball,’ he said. ‘They’re leaving now.’ The woman described the vehicle and read out the registration number as the driver edged the car back into the traffic.

‘Anyone else have eyeball?’ asked Aspden.

‘Bravo One, I have eyeball.’

That was a close call,’ said Aspden. ‘All right, everybody. Bravo One has eyeball. Note that Tango One is now a blue Transit van with at least two IC Four males on board.’

Charlie Two accelerated away, putting plenty of distance between themselves and the van.

The driver of the blue Transit van was a British-born Asian. He had no idea whom he was driving or what was in the case they had loaded into the back. He had been told where to meet the men, and where to go, but that was all. His name was Rahman Naeem but only his parents used his given name. His friends and colleagues called him Ray. The van belonged to his father but it was usually Naeem who drove it, running to the cash and carry to restock the family’s corner shop in Leyton.

Naeem’s instructions had come through his imam, a seventy-year-old cleric who had fought against the Russians in Afghanistan but who had lived in England since the early eighties. He was a learned man and knew the Koran by heart, but he had never lost his warrior roots. He had groomed half a dozen men at the mosque, initially tutoring them in the Koran but then educating them in the politics of Islam. Only those he trusted totally were admitted into his inner sanctum of students where he explained the aims and objectives of Islamic State.