A teenager accused of stabbing a 15-year-old Alan Cartwright to death for his bike was seen laughing as he cycled away from his dying victim, a court heard.

Joshua Williams, 18, was allegedly caught on CCTV as he carried out the “utterly senseless” murder of Alan Cartwright who was riding with his friends in Caledonian Road, Holloway, on February 27.

Alan was stabbed as a group of three males carried out a “pincer movement” to rob them of their bikes in a seven-second attack caught on shocking CCTV footage, the Old Bailey was told.

He made a desperate attempt to escape after the knife punctured his lung, but collapsed and died a few yards up the road.

Williams, of Davenant Road, Upper Holloway, was seen “crying hysterically” and carrying a Bible when he was handed in to police days later by his own parents to apparently confess to the crime, jurors heard.

But moments after the deadly attack the three teenagers who carried out the robbery of the two bikes Alan’s friends were riding were seen laughing as they fled the scene, it was claimed.

Edward Rowland, who was walking south along Caledonian Road with his account manager friend, Matthew Hopwood, said he noticed three males pointing to the other side of the road.

He noticed one of them run across the road towards the west footway in what prosecutors say was the beginning of the attack.

“Two bikes came across from the other side of the road and initially cycled into oncoming traffic,”said Mr Rowland in a statement read in court.

“They were going quite fast and they seemed to be laughing.”

Williams allegedly jumped onto the back of the bike stolen from a teenage girl who was cycling with Alan, while their 17-year-old accomplice escaped on a cycle stolen from another of his friends.

Jurors have heard Shaquille Roberts, 19, and a 17-year-old boy have already pleaded guilty to robbery for stealing bikes of two of Alan’s friends.

Williams claims he was elsewhere at the time of the incident and denies murder and conspiracy to rob.

The trial continues.