‘Zoom in… there, that one,’ said Gabriel, pointing at a flat costing seventy-one pounds a night. Bose zoomed in closer. The flat was in the block of flats in Stonebridge Park.

‘Got him,’ said Gabriel.

The flat’s host was called Helen, who described herself as a bubbly lady always happy to help. ‘Sounds like a dating app,’ muttered Gabriel. ‘Have we got a number?’

‘Just an email address, ma’am. I’ll get someone on to Airbnb now.’

Gabriel looked up. One of the screens was showing the live match from Wembley. Kick-off was in twenty-four minutes.

#

Special Operations Room, Lambeth, London

Tennant turned to the team sitting alongside him.

‘Give me an update on anti-drone tech.’

‘MOD say they’ve nothing suitable within London right now,’ said the drone expert, Amanda Elliott. ‘Our electronic jamming gear is now in Wembley.’

‘And snipers?’

The Gold Commander pulled up a satellite image of Wembley on the video screen. ‘We’ve got them in position on the roof here and here, and on strategic rooftops along the routes of the march and marathon. But they’re spread thin. As a last resort, the procedure is to try to shoot down the drone before it reaches a crowd. Frankly, boss, it’s a desperate tactic, but any location away from the crowd is better – over the car park or top of the building would be best.’

‘Understood,’ said Tennant. ‘A drone falling into a crowd is preferable to one exploding into it. Let’s just pray that’s not a choice they have to make.’

#

Stonebridge, North West London

The buzz of a police helicopter scanning the streets and rooftops had been a constant background noise for Abu Mujahid for the last half hour, but his two drones were hidden out of sight from above under a patio table. He recalled that first visit to the flat when he’d measured the door frame of the French windows and the space on the balcony to ensure they would fit. Little details, his trainer had told him years before. Little details – they’ll make you or break you.

Semtex, the bag of nails and the radio control relay were firmly taped to the drones. Saleem was giving them the final check over. The two smartphones he’d bought were connected to the remote-control units on the kitchen table.

The original plan, devised in Syria in those long evening talks with the GID leaders months ago, was for the drones to follow a preprogrammed course. They could be released and sent on their way with no human involvement, leaving Abu Mujahid to get out of the flat and into a safe house.

But the tests of the software in the Lake District had not gone well. The software was unreliable. And besides, he and Saleem wanted to be part of the day, not spectators. So last night they’d made the decision to launch the drones on a preprogrammed course, but then take over the controls for the final descent into the stadium. They would each have one drone. Saleem would take the first, and detonate it immediately after kick-off at 3pm. Abu Mujahid’s would follow. He would wait for the perfect moment – when the crowds were densely packed at the exits – before flying in the second drone from a holding position above wasteland near the stadium, and creating the largest death toll.