‘Ma’am,’ said the DS. ‘The second unit have just reported that an ambulance was driving away from the house when they approached. About five minutes ago. We believe that the suspects may have been inside.’

That’s it, thought Gabriel. It made perfect sense. How do you get a vehicle through the security cordon of a high-security event outdoors and then abandon the vehicle and walk away without raising suspicion? Impossible if it’s a car or ordinary van. But what if it’s supposed to be there? What if it was a St John ambulance? And the words of the texts that Rod Houghton sent to his NRF operative in Leeds came back to her. Pitch confirmed. And what was the other one? On rota as passenger. Will bring driver to house and swap there.

So that was the plan, Gabriel thought. Get someone to infiltrate St John Ambulance, posing as an ordinary volunteer, do the training, put in the hours, then get on the rota as an assistant for today, somehow lure the driver down to this house, then cosh him and replace him with the second person. They’d need the uniform and ID – so that’s why they removed the poor sod’s top.

But they had the licence plate of the ambulance. And that meant they could use the network of Automatic Number Plate Recognition cameras to trace its path through the city.

#

New Scotland Yard, Victoria Embankment, London

‘What’s the plan?’ said Tennant down the phone line.

‘The unit passed the ambulance minutes before they arrived at the house and caught its licence plate on the dashcam,’ said Gabriel. She had moved to a quiet, windowless side office off the control room. ‘ANPR has picked up the ambulance heading north-east towards Roundhay Park. It’s normally a twenty-minute drive, but the traffic is bad today, so it’s more like forty minutes. The goal is to stop the ambulance half a mile from the park. Forensics are at the house in Armley, and early indications from some of the packaging and residues they’ve found in the kitchen suggest an old-school fertiliser bomb.’

‘Any indication if it’s a suicide bomb or a conventional car bomb?’ said Tennant.

‘Could be either, sir.’

‘And could they detonate the explosive en route if they detect they are being followed?’

‘We can’t rule it out. A surveillance car is in position behind the ambulance and a firearms team should be joining the pursuit any moment. Right now, all we can do is keep our fingers crossed.’

#

Leeds

Sergeant Sameer Rehmann weaved his way down the dual carriageway in the direction of Roundhay Park. The blue light, normally hidden in the grille of the anonymous SUV, was on, and he made good progress. His three passengers were silent and Rehman knew what they were thinking. In a speedily arranged operation like this, there were so many uncertainties. They did not know how the target was armed, if the van was booby-trapped, how the explosives were rigged to go off. In these nervy moments, the desire to ring home or leave a message on their partner’s mobile was overwhelming. He’d done it a couple of times himself in the early days, but had stopped when he realised the messages caused more alarm than comfort.