Try to imagine what must have been going through their feverish adolescent minds. It was June 29 last year and two young boys who had met over the internet set out from Altrincham, Greater Manchester, each with murder secretly in their thoughts.

They were embarking on a plot that ended last week in one of the most extraordinary cases ever to come before a British court. The older one, known for legal reasons as Mark, was 16 and had never been in trouble before. But after months of e-mail communication with mysterious characters in internet chat rooms, he believed that he had been given a licence to kill. He was a British secret service agent, number 47695. His mission: to stab his friend.

That friend was 14 years old at the time and known in the court case as John. He was a bright grammar school boy from a middle-class family and was expected to go to university. But he was also lonely and confused, having fallen out with schoolfriends and his stepfather. For him, Mark was a special older friend, one with whom he had a quasi-sexual relationship.

As the two walked into a shopping centre, Mark said casually that he had to “pick up a knife”. First he withdrew £10 from a cash machine and then they went into a Boots store where he asked John to pick out a suitable implement.

“By asking him to pick out the knife I think I was making it easier for him,” Mark later told police, according to prosecutors. John chose a 6in Sabatier and they bought it together.

To Mark it was all part of his orders, delivered through cyberspace, to help “British intelligence”. But John, too, had a secret: he knew Mark was planning to stab him — because he was the person who had arranged and ordered the killing in cyberspace.

According to documentation presented in court, Mark was feeling sick and dizzy. “I started to get visions in my head,” he later told police. “The visions were becoming more frequent. I had a feeling of knowing that I had to stab someone which came from the visions.

“Whilst I sat with (John) . . . I tried to tell him how I was feeling.” He apparently told the younger boy that he “might have to do something” that day.

John knew exactly what that “something” was but gave nothing away. Instead the boys headed for a wooded area where Mark told his friend that he had to stab him.

“You’ve got to let me do it,” he said, according to prosecutors. On several occasions over about an hour he held the knife close to John’s body. What was the younger boy thinking? Was he secretly waiting to see if his friend would go through with it? Did Mark believe that the younger boy thought he was only larking around? They returned to Altrincham and then went to a McDonald’s where they bought a Coke before heading to an alleyway in an area known as Goose Green. It was about 8pm. According to prosecutors, the younger boy later testified from hospital: “He (Mark) said I was his best mate and pushed the knife in. I said ‘No, stop’. He pushed it in. I started to scream. He said, ‘Calm down, don’t let anyone hear us’.”

The older boy later told police: “I was not in control. I did not even feel like me. I put the knife to his stomach and pressed down on it.

“The knife went into him and he started bleeding through his top. I hugged him as I did not want to hurt him. Then I put the knife into him again.”

Despite having committed the stabbing, Mark called the police, who arrived within minutes to find John lying critically injured. He was taken to hospital with wounds to his kidney and liver, but survived.

Explore UK News

• Crime News

• Education News

• Health News

• Scotland News

Times Recommends

• The bright side of this winter rain
• Story behind the picture: Snow Leopard, 2008
• Times Charity Appeal: The Place2Be