CCTV footage of the moment a teenage boy was stabbed to death on a busy north London street has been released by police in an appeal for witnesses.

Alan Cartwright, 15, can be seen cycling along Caledonian Road, Islington, north London, with three other boys when a hooded individual steps out into the busy street and stabs him in the chest at 7.34pm on 27 February. Two other individuals in the footage are apparently accompanying the attacker.

Two of Mr Cartwright’s three companions are also accosted by the three youths. They are pulled off their bikes, which are used by two of the suspects to flee the scene. Th e injured teenager continued along Caledonian Road for a short distance before he collapsed near the junction with Twyford Street.

Police and London Ambulance Service were called to the location but Mr Cartwright was pronounced dead just a short time later.

A post-mortem on 2 March confirmed the cause of death as a single stab wound to the chest.

Detective Chief Inspector Chris Jones, who leads the investigation for the Homicide and Major Crime Command, said: “The footage of the suspects attacking Alan and his friends is truly shocking.

“Alan stood no chance of defending himself against his attacker who casually stepped out in front of him and stabbed him in the chest.”

Det Chief Jones said identifying and arresting the three suspects was the force’s “absolute priority.”

The first suspect is described as a male youth, thought to be white, of slim build. He is believed to have been wearing grey or dark coloured hooded top, dark bottoms, which may have contained a keychain hanging from the rear pocket, and wore an item of clothing obscuring his face.

The second suspect was a black male youth, slim to medium build, wearing a sleeveless jacket with a hoodie underneath. He wore a shoulder bag across his body and similarly to the first suspect had an item of clothing across his face.

The final suspect was of medium build, wearing a three-quarter length coat with a trimmed hood, and a dark top decorated with a multi-coloured motif on the chest. He wore lighter bottoms and dark shoes.

Det Chief Jones officer appealed to anyone present on the busy road at around that time to contact them, should they have seen anything. He added police were also looking for information around the two bikes stolen at the scene.

One of the bikes was red, with black electrical tape on the frame, and was a ‘Specialized Hard Rock’ mountain bike. The second, a red and black ‘Specialized Vita’ pedal cycle, had a red stripe and the word ‘Specialized’ in white stencilled on the frame.