A man has been arrested on suspicion of the murder of teenager Alan Cartwright, who was stabbed to death while riding a bicycle with his friends.

Police said an 18-year-old man was arrested in the early hours of today after attending a north London police station.

Alan's family yesterday appealed for witnesses to come forward after the 15-year-old was killed on Friday in what was described as a "senseless" attack.

CCTV footage was released yesterday as part of the appeal.

Alan managed to continue cycling a short distance after the attack on Caledonian Road in Islington, north London, but soon collapsed and was pronounced dead at the scene later.

His mother and sister described the Army cadet and Celtic and Arsenal fan as a "joker" who loved bikes and never caused any trouble.

Fighting back tears, Alan's mother Michelle Watson, 39, said: "He always made you laugh about anything and everything. He was just the funny one out of his friends.

"I feel angry, I want somebody found for this. I just feel numb."

In the CCTV footage, a suspect is shown lunging at one of Alan's friends and knocking him off his bike.

Another male is seen crossing the road and grabbing another friend to pull him off his bike.

A post-mortem examination on Monday concluded that the cause of Alan's death was a single stab wound to the chest.

Detective Chief Inspector Chris Jones, who is leading the investigation for the Homicide and Major Crime Command, said yesterday: "Alan, in my mind, was not a gang member and was purely a 15-year-old boy cycling with his friends on a Friday night at 7.30pm."