Al-Hussain took it off and handed it to him. Al Am looked at it and turned it over. As he did so, al-Hussain remembered the engraved inscription on the back: ‘To a wonderful son, from his proud parents. May Allah protect him.’ Al Am looked at him and shook his head.

‘I understand,’ said al-Hussain.

‘And the bag. We must take it from you now.’ He held his hand out for al-Hussain’s backpack. He took it off and held it for a while, like a newborn baby, cradled against his chest, his head resting on the top. He didn’t want to let go of his weapon, but knew he had no choice. If he was discovered with a sniper’s rifle, his cover would be destroyed and he’d be shot or worse. The notebook had to go. In fact everything, every single thing, that connected him to his former life had to be handed over to the IS fighter. To keep anything that gave away his true identity risked exposing him and ending the mission. And the mission was all that mattered.

‘You will take good care of my bag,’ said al-Hussain, as he took it off. ‘You will take it back to Commander al-Lihaib. You are to give it to him and no one else.’

‘I will do that,’ said Al Am. ‘Inshallah.’ If Allah wills.

Al-Hussain held out the bag. His fingers stayed touching the nylon material for several seconds and he sighed audibly as it was taken from him. ‘Now tell me your name,’ said Al Am.

‘My name?’

‘Who are you?’

Al-Hussain frowned. ‘I am Mohammed al-Hussain.’

Al Am shook his head. ‘You are not. From now on you are Hammad Rajput. From England. Until this mission is over you must put all thoughts of Mohammed al-Hussain out of your head.’

Al-Hussain grimaced at his mistake, but said nothing.

Al Am placed the wristwatch inside the bag, then slung it over his shoulder. ‘It is time to go.’

‘Thank you for getting me this far.’

‘It has been an honour and a privilege,’ said Al Am, bowing his head.

Mohammed al-Hussain was put into the back of a rusting black pick-up truck. The two IS fighters who had driven him from Palmyra sat in the front and he was joined by another man, in his late twenties with skin burned almost black by the sun, who cradled an AK-47 with a folding metal stock in his lap. He turned to al-Hussain and smiled, revealing several missing teeth.

‘Assalamu alaykum,’ said the man. ‘Kayfa anta?’ How are you?

‘Bi-khair alhamdulillah.’ Fine, praise be to Allah.

‘There’s water under the seat if you’re thirsty.’

Al-Hussain nodded. ‘I’m grateful, thank you.’

Shepherd had the black cab drop him outside Selfridges. He went inside and spent fifteen minutes wandering around, reassuring himself that he wasn’t being followed. He headed outside and grabbed the third cab that drove by with its light on and said, ‘Paddington station,’ in a loud voice as he climbed in. As soon as the vehicle pulled away from the kerb he asked the driver to drop him at the Mayfair Hotel.