Police have released CCTV footage of the moment a 15-year-old boy was fatally stabbed while he was cycling with friends.

Alan Cartwright, from Islington, north London, was attacked near Copenhagen Street in the borough, last Friday.

The teenager managed to cycle away but collapsed on nearby Caledonian Road and was pronounced dead at the scene.

Det Ch Insp Chris Jones said: "The footage of the suspects attacking Alan and his friends is truly shocking.