A teenager who allegedly stabbed 15-year-old schoolboy Alan Cartwright to death for his bike was turned in by his mother, a court heard today.

The court was told Joshua Williams, 18, was caught on CCTV as he allegedly carried out the “utterly senseless” murder of Alan Cartwright who was cycling along Caledonian Road, Holloway, on the evening of February 27.

Williams, of Davenant Road, Upper Holloway, was seen “crying hysterically” on the morning of March 4 when his mother handed him in to Islington police station, the jury was told.

The court heard that he was arrested for murder and as he left the interview room, Williams asked an officer: “It’s the right thing to do isn’t it?”

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

But the prosecutor told jurors: “One can readily understand how a young man coming to terms with having stabbed someone to death might initially have been persuaded that the right thing to do was to hand himself in before subsequently losing his courage when faced with the enormity of the consequences.”

Alan was at the head of a group of four youngsters when they were attacked.

Mr Rees said three males were ahead of them and “decided to rob them of their bikes”. He continued: “The robbery was brazen and swiftly executed, taking place in front of motorists and pedestrians. It was over in a matter of seconds.”

Jurors heard Shaquille Roberts, 19, of no fixed address, and a 17-year-old boy have pleaded guilty to robbery for stealing bikes from two of Alan’s friends.

Mr Rees said the third robber, who the prosecution claim was Williams, stepped out into the road and stabbed Alan in the upper left part of his chest in a “deliberate and gratuitous stabbing.”

The trial continues.