A teenage boy was seriously injured when he plunged nearly 50ft from a rope swing into a ravine in remote woodland.

Emergency services spent nearly two hours trying to locate the teenager after the rope attached to a tree snapped.

The 18-year-old youth, who has not been named, was playing with a friend in St Leonard's Forest, near Horsham, when the accident happened on Saturday night.

The friend scrambled down the ravine and pulled the youth from a stream but was unable to move him any further.

He ran nearly a mile to the nearest road to flag down a passing motorist.

Paramedics treated the boy at the scene for leg, arm and shoulder injuries before helping to carry him on a stretcher half a mile to the ambulance.

He was taken to the Princess Royal Hospital at Haywards Heath.

The teenager has not been named by Sussex Police, who operate data protection guidelines.

Station Officer Dave Dickson, who co-ordinated the West Sussex Fire Brigade's response, said: "The extensive local knowledge of the firefighters enabled the emergency services to pinpoint the casualty with the minimum of delay.

"It is apparent that he had been lying injured for some time in considerable pain."

He said paramedics stabilised the teenager's condition and firefighters then assisted in carrying him to the nearest road.

A spokesman for the Sussex Ambulance Service paid tribute to the passing motorist who was flagged down.

She said: "A member of the public was flagged down by a friend of the patient. He was very helpful.

"There was a very bad mobile phone signal in the area so he drove to another area where the signal for his phone could be received and he called the emergency services.

"Then he went back to check on the condition of the boy before driving back to where he had a signal and spoke to us again.

"His call enabled us to send the most appropriate resources.

"This member of the public was a great help."