‘What is it with the leaves they chew?’ he asked.

‘That’s khat. It’s a stimulant.’

‘And it’s allowed? They are Muslims, right?’

Hussain chuckled. ‘They are Muslims but they are Africans. They don’t know any better.’

‘But they are shahids. They must go to meet God in a state of purity and cleanliness, surely.’

Hussain lowered his voice, even though he knew that the two Somalis could not understand Urdu. ‘They do not know, brother. They think that the bomb is going to be detonated by a mobile phone. They do not know that it is on a timer.’

‘And they will die without knowing?’

‘Inshallah,’ said Hussain.

‘Because they cannot be trusted?’

‘They are Africans, brother. Who can trust an African? You have to count your fingers every time you shake hands with them.’

He turned and flashed Crazy Boy a beaming smile. ‘We are ready,’ he said. ‘Everything is done. Help us close the doors.’

Charlotte Button paced up and down behind the technicians. On the screens on the wall behind her were six CCTV feeds showing the progress of the truck along the M3. One of the screens showed the truck leaving the M3 at the Basingstoke turn-off and since then there had been no sightings.

‘Come on, everyone, let’s find it,’ she said, even though she knew they were working flat out and that the lack of success wasn’t for want of trying. She rubbed her hands together and looked across at Shepherd. ‘At least Basingstoke probably isn’t the target.’

‘You don’t know that,’ said Shepherd. ‘You heard what Dr Wilson said, a dirty bomb anywhere in the country brings the economy grinding to a halt. And London is always going to be a harder target because . . .’

He was interrupted by one of the male technicians, who raised his hand. ‘I have a hit,’ he said. ‘Camberley, thirty minutes ago.’

‘Heading north?’

The technician nodded and put the recording on to one of the large monitors. The truck was in the inside lane, hemmed in by heavy traffic.

‘They must have stopped off in Basingstoke and started their journey again,’ said Button. She went over to a large-scale map of the country, tapped the M3 and ran her finger along it to the M25. ‘They’re probably on the M25 already,’ she said. ‘I need a live feed and I need it now, please.’

Liam was lying on the sofa watching an episode of Two and a Half Men on the television when Katra popped her head around the door. ‘Are you OK?’ she asked.

‘Fine.’

‘Homework all done?’

‘Sure,’ he replied, his eyes never leaving the screen.

‘Do you want to go and play football?’

‘With you?’

Katra grinned. ‘What, scared to play a girl?’

‘It’s not that,’ said Liam.

‘You need some exercise,’ said Katra. ‘It’s not good to lie around all day.’

Liam pulled a face.

‘OK, what about going shopping? We can go to the Maylord Centre.’

‘I don’t need to buy anything.’