Crazy Boy shrugged. ‘Go back to Somalia,’ he said. ‘I have no choice. They’ll take everything from me here.’

‘They can’t force you to leave,’ said Two Knives. ‘You’re British.’

‘But they can put me in prison,’ said Crazy Boy. ‘They can take away everything I have.’ He slotted more leaves into his mouth and chewed as he watched the two men in the container. ‘Whatever you do, you shouldn’t stay in London,’ he said. ‘Go north, at least fifty miles.’

‘You said there wouldn’t be an explosion.’

‘There will be a small explosion, but the wind will carry the radiation for many miles.’

‘I will come with you, brother,’ said Two Knives.

Crazy Boy grinned and pulled two airline tickets from his back pocket. ‘I had assumed that you would.’ He patted Two Knives on the back. ‘It will be like the old days,’ he said. ‘Taking ships and making the infidels pay. And out in Somalia no one can touch us. We will be kings again.’

Two Knives nodded and helped himself to more khat.

‘It’ll be good to get back,’ said Crazy Boy. ‘England was making me soft. I know that now. I’ll never be soft again.’

Shepherd put down a cup of tea in front of Button and she smiled her thanks. He sat down opposite her and sipped his coffee. CCTV images from around the country were flashing across the monitors as technicians worked away on their computers.

‘I didn’t realise that you could do this,’ said Shepherd, gesturing at the screens. ‘Use automatic number plate recognition on CCTV feeds from anywhere in the U.K.’

‘Since 2006,’ said Button. ‘We have feeds from the motorways, main roads, all the council systems, the ring of steel around the City, down to petrol station forecourts. And we’ve got feeds from mobile police CCTV units. All the feeds are run through the National ANPR Data Centre at Hendon.’

Shepherd nodded. Hendon in north London was the site of the Police National Computer. ‘That must be thousands of cameras,’ he said.

‘And every single one can be scanned for a specific plate,’ said Button. ‘The computer stores fifty million records a year. And we have total access.’ She smiled. ‘It really is Big Brother, actually. The government can cross-reference registration numbers with MoT test certificates and insurance companies and flag any vehicle that shouldn’t be on the road. Not that MI5 does that, of course.’

‘Not yet, anyway,’ said Shepherd.

‘The point is, Spider, police forces around the country and our good selves have instant real-time access to every single camera with the ability to pick out a single specific vehicle.’

Shepherd gestured at the technicians. ‘So why aren’t they pulling out any needles from the haystacks?’

‘It takes time,’ said Button.

‘How long is this information stored for?’

‘Five years,’ said Button.

‘Do you mean that you can track everywhere a vehicle has been over the past five years?’