The plane eventually landed at Northolt. Danny and Kate were still gazing at his laptop as they boarded a helicopter on the tarmac, bound for a Cobra meeting in London.

It was MI5 who eventually found the missing link: CCTV footage from a dry cleaner revealed that, just by a roundabout, the gangsters had pulled over a for a few seconds to perform a very slick changeover, switching their cargo – now prostrate in body bags – into the back of a lorry. ‘They’re dead,’ Kate shouted, against the noise of the helicopter.

‘Unconscious,’ Danny said. ‘They wouldn’t move them any other way.’

They began the process of tracking them again, this time to an industrial park on the outskirts of Luton. It was Danny who got there first, just before they ran from the helicopter to a waiting car at Battersea heliport.

Danny got into the back beside Kate. Julie was in the front, Ian in a car behind with Suzy. ‘We can’t risk a rescue,’ Danny whispered to Kate, as the car roared away.

She looked at him, confused.

‘The moment they hear the rotors, they’ll kill them.’

Kate’s phone buzzed. She opened a video from Fiona’s WhatsApp account. It showed her daughter’s terrified gaze for only a moment, before her face was pushed down. Someone held up a huge blade and began the process of beheading her.

Kate screamed, dropped the phone.

Danny picked it up. ‘It’s fake,’ he yelled, above the sound of the rotors. He gripped Kate’s shoulders, looked her in the eye. ‘They’re screwing with us. It’s fake!’

‘No . . . No . . .’

‘Look at it. Look at the quality of the pictures. I told you! There’s a weird sheen to those images.’

Kate could not bring herself to examine the footage. Julie turned. ‘What about the sewers?’ She put her computer on Danny’s lap. On it was a planning application that detailed the sewage arrangements for a huge industrial park.

Danny nodded. ‘They’ll expect another airborne rescue. They probably left someone behind to see what happened at the place the other van went to.’

‘I’ll text Ian.’

Kate was too paralysed to think straight. ‘I don’t know . . .’

‘It’s the best way, Kate.’ Julie turned to her again, vivid green eyes staring into Kate’s own: firm, friendly, certain. She radiated steel and confidence. ‘We have your back.’

They reached Whitehall and were whisked down the stairs towards the Cobra room in the Cabinet Office. But as they reached the last security barrier, Ian turned to her. ‘You can’t come in, Kate.’

‘What do you mean?’

‘They are your children. We can’t allow you to be in the meeting.’ His manner was kindly, reassuring. ‘We’ll do everything we can. Julie’s idea is a good one. The director of Special Forces is looking into it right now.’

‘No, I have to be in there—’