A fairground ride company has been fined thousands of pounds after a teenager was thrown from a ride at Sonisphere, suffering life-threatening injuries.

Perrin Stevens Ltd, along with its director and two ride assessors, admitted breaching health and safety regulations after a 15-year-old boy came free from his harness on the Orbitor Extreme ride while at the Knebworth Park music festival in August 2009.

The boy was one of the first to use the ride – on its third outing – when he was propelled from the ride and through steel perimeter fence panels.

He was taken to hospital with life-threatening injuries after tearing his aorta artery in the incident, as well as breaking ribs, his shoulder, and shattering his ankle.

The young rider spent a week in hospital, and later had to have his ankle pinned.

Following an investigation the Health and Safety Executive (HSE), those responsible were sentenced on Friday after breaching the Health and Safety at Work Act.

Inspectors told Cambridge Crown Court that their investigation uncovered a number of serious defects which were not picked up at any of the ride’s design, testing or sign-off stages – all of which are required by law. This included the failure to make an adequate analysis that the restraint system was of suitable dimensions to hold typical riders.

Numerous discrepancies in the documentation for each stage also revealed design, design review and initial test processes had not been carried out adequately – resulting in the eventual use of an unsafe ride.

Manufacturing company Perrin Stevens Ltd, based in the Farlington district of Portsmouth, was fined £2,000 and ordered to pay costs of £3,000 after pleading guilty to the breach.

The business’ director Perrin Stevens, of Oakley Green Road in Windsor, was fined £3,000 and ordered to pay costs of £3,000.

Ride assessors Martyn Lacey, of Main Road in Nottingham, and Frederick Meakin, of Stretton Road, Rutland, were both fined £8,000 and ordered to pay costs of £10,000 each.

Following the sentencing, HSE inspector Stephen Manley said: “Fairground machinery is designed to provide people attending fairs with an exciting, fun time without exposing them to serious danger. There are defined procedures to follow to make sure rides are safe when they are designed, built and used. These must be respected at all times, as they are by the majority of operators in the industry.

“In this instance, not one of the parties involved properly fulfilled their duties, and the outcome was a very serious but entirely preventable incident, which could easily have cost a young teenager his life.

“Luckily, no one died this time, but this incident should serve as a lesson to fairground owners, ride manufacturers and examiners that cutting corners is unacceptable and will lead to putting lives at risk.”