Naeem had been one of the imam’s star pupils and had begged to be allowed to go to Afghanistan for further training but the imam had advised him against it. Any young British Asian who travelled to that part of the world was immediately placed on the government’s watch list. The imam had explained that Naeem would be more valuable as a cleanskin: he could operate without ever being watched. Over the past year the imam had used Naeem half a dozen times, usually driving people or delivering parcels, sometimes passing messages in person. Naeem never asked whom he was driving or what he was delivering: he trusted the imam completely.

Naeem kept a close eye on his mirrors, checking the vehicles behind him constantly. The imam had introduced him to a man from Birmingham, who had taught him about counter-surveillance, how to see if you were being followed and how to lose a tail. Naeem varied his speed, took random turns without indicating and accelerated through amber lights.

He took a circuitous route to his destination, at one point making four left turns in a row, and stopped off at a filling station, ostensibly to put petrol in the tank but the real reason was that it gave him plenty of time to look around for followers.

Only when he was satisfied that he was not being tailed did he head for the destination.

The police van braked suddenly, throwing Shepherd off balance. ‘This is you,’ said Singh. ‘Break a leg.’

‘Thanks for the lift,’ said Shepherd, getting up.

Singh opened the rear door and Shepherd got out. The door closed almost immediately and the van drove off. A few yards in front of him, Thomas Leigh was at the wheel of a black SUV, with Roy Graves, the senior of the three SFOs who had been at the house in Ealing, in the passenger seat. Graves flashed Shepherd a thumbs-up and waved him over.

Shepherd jogged across to the SUV and climbed into the back next to the third member of the team, Neil Walker, a former squaddie who had done two tours in Afghanistan before joining the Met.

‘Nice of you to dress for the occasion,’ said Graves, as Leigh pulled away from the kerb.

‘I was at the boxing,’ said Shepherd.

‘The Hughes-Kuznetsov fight?’ asked Walker.

‘I think they’re calling it the Kuznetsov-Hughes fight.’

‘Bollocks,’ said Walker. ‘Hughes’ll walk it. And you’ve got tickets?’

‘Ringside,’ said Shepherd.

‘Not your day,’ said Walker. He handed Shepherd a transceiver.

‘So, sitrep,’ said Graves, from the front. ‘The tangoes switched vehicles in the Westfield car park. We assume the gun is on board but no one saw the transfer. The tangoes are now being very cagey so something’s going on. They’re in a blue Transit heading east.’

Shepherd put in the earpiece. ‘Bravo One, fall back and let Bravo Two have eyeball,’ said Aspden.

‘How far away from the bravos are we?’ asked Shepherd.