A teenage cyclist was airlifted to hospital with head injuries after somersaulting over his handlebars on Hampstead Heath.

The 16-year-old had been chatting happily with friends only moments before he careered down Parliament Hill and crashed his BMX bike at around 5.30pm on Sunday (May 13).

A police source said the teenager was believed to be riding someone else’s bike and had not been cycling on a designated path.

Emergency services scrambled the London Air Ambulance as friends reported the victim was slipping in and out of consciousness.

The helicopter landed meters from the crash site and ambulance crews also attended the scene.

The teenager was strapped to a stretcher and flown to the Royal London Hospital in Whitechapel, where he was treated for his injuries.

Lewis Dediare, who was flying his kite on Parliament Hill, had been talking with the teenager and two friends only moments before the crash.

Mr Dediare, who works for a telecoms firm in Regent’s Park, said: “He and his friends had come over to ask me about kite-flying and then only a few minutes later I saw the helicopter flying towards the Heath which made me think something serious was going on.

“When I got there I saw his friends down by the crash site and they seemed pretty shocked.

“He had probably fallen into a little dip in the ground and been thrown off his bike – it’s a very uneven surface there.

“The ambulance crews were being very careful with him, they were obviously a little worried. It did look quite serious.”

The Hampstead Heath Constabulary hosted a cycle safety day to encourage cyclists to use marked paths on the day the accident happened.

Officers handed out cycle safety leaflets and diaries to more than 100 people.