08/09/2015 12:26 BST | Updated 08/09/2016 06:12 BST

Teenager Goes On Trial Over 'Gratuitous' Stabbing Of Boy, 15

A teenager has gone on trial for the "deliberate and gratuitous" stabbing of a 15-year-old boy who just happened to be cycling by with his friends when he was targeted by robbers.

CCTV images captured the moment when Alan Cartwright was fatally injured in Caledonian Road, north London, in February this year.

The prosecution say 18-year-old Joshua Williams was the boy who lashed out with a blade as he and his friends moved in a pincer motion to unseat the riders and make off with their bikes.

But despite bleeding from the knife wound, Alan kept on riding until he collapsed and died outside a swimming pool, the Old Bailey heard.

Opening the trial, prosecutor Jonathan Rees QC said: "Alan's death attracted significant media attention at the time.

"Not only was it another tragic example of the knife crime that blights our society, but this particular stabbing was captured on a local borough CCTV camera which revealed that at the time he was stabbed, Alan was doing nothing more than innocently riding his bike with his mates."

Mr Rees told jurors that Alan was studying at college and was described by friends as a "harmless person who avoided confrontation".

But on the evening of February 27, he was cycling in Caledonian Road, north London, with five friends when three youths intercepted them.

Mr Rees said the "robbery was brazen and swiftly executed" as in a matter of seconds, they stepped out in front of the cyclists and managed to take two bikes.

The prosecutor went on: "The CCTV shows that the third robber stepped out into the road towards Alan and swung his left arm towards the upper left part of Alan's chest.

"The events that unfolded clearly establish that when he swung his arm towards Alan, the third robber had a knife in his left hand. This was a deliberate and gratuitous stabbing.

"Despite being mortally wounded, Alan did not come off his bike at that point and he managed to cycle on before collapsing a short distance up the road outside the Cally swimming pool."

A staff member at the pool gave the boy first aid before police and paramedics arrived but Alan was declared dead at the scene a short time later.

Jurors were told that the main issue in the case was the identity of the third robber who the prosecution say is Williams, although the defendant says he has an alibi.

Williams, who lived with his family off Holloway Road, north London, was "crying hysterically" when he was brought to Islington station on March 4 with his parents.

When asked why they were there, his mother told an officer it was about the incident in Caledonian Road, saying "Yes, he's involved, he did it."

The defendant denies murder and conspiracy to rob and the trial continues.