Hassan had been an eager pupil and had returned to Salford fired up and ready to fight for the cause, to kill the infidel and avenge Muslims who had been persecuted and murdered around the world. His instructions had been to return to his regular life until he was called upon to serve the cause. Each day he was to check a Yahoo account that had been specially set up for him. He was not to send emails from the account, or to receive any on it, but messages could be left in the drafts folder. It was a foolproof system that neither the Americans nor the British could spy on, no matter how hard they tried. Messages that were not sent could not be intercepted. But days turned to weeks, weeks turned to months and eventually became years. Each day he would check the drafts folder, and each day he would be disappointed.

When the Americans killed al-Qaeda leader Bin Laden, Hassan was sure he would be called to arms, but the call never came. What he didn’t know was that after Bin Laden’s death there had been a leadership struggle for control of the jihadist battle in the Middle East, with the relatively young jihadists of Islamic State eventually becoming dominant. The men who had trained Hassan had switched sides early on and expanded their training programme. Dozens of young jihadists were trained and sent back to their own countries, and still Hassan waited. Several times he would leave a message in the draft folder: I AM READY. PLEASE USE ME. Each time, the reply was always the same: BE PATIENT, BROTHER.

Eventually, some five years and six months after his return from Pakistan, Hassan received a message telling him to report for a meeting in Heaton Park the following day. After he’d read it, Hassan could barely concentrate on his work, servicing engines at the family’s garage. He couldn’t eat because his stomach was churning, and that night he tossed and turned, unable to sleep.

He walked past the entrance, then doubled back, checking carefully to see if he had wrong-footed any followers, but he was sure he wasn’t being tailed. He went into the park.

Heaton Park covered more than six hundred acres and was the biggest council park in Europe, with an eighteen-hole golf course, a boating lake, tennis courts, woodlands, ornamental gardens and a petting zoo. The instructions said that Hassan was to wait on a bench overlooking the lake. He did a complete circuit of the lake, then sat down on the bench. Two minutes later he was joined by an Asian man in his fifties, bearded and wearing a skull cap. In his right hand he carried a small copy of the Koran. He had the look of an imam. He undid the top two buttons of his coat and sat down on the far side of the bench. They were silent for a minute or so. Then: ‘Did you see the match last night?’ said the man, quietly, as he looked out across the lake.