The owner of the Alton Towers theme park has been fined £5m ($6.4m) after pleading guilty to breaching health and safety standards following the Smiler roller coaster crash which left 16 people injured, including two teenage girls who each needed to have a leg amputated.

Merlin Attractions Operations Ltd admitted that failings on their part caused the crash on 2 June 2015 which was described in court as being the equivalent to a family car crashing at 90mph.

During a two-day hearing at Stafford Crown Court, Judge Michael Chambers QC said "human error" was not the cause of the horrific crash, but added it was still "needless and avoidable accident" caused by a "catastrophic failure" of safety. The judge added the fine could have been as high as £7.5m had the incident gone to trial.

Leah Washington and Vicky Balch, from Barnsley, each had a leg amputated after being involved in the roller coaster crash. Balch's then boyfriend, Daniel Thorpe from Buxton Derbyshire, also suffered a broken leg and a punctured lung. Washington's boyfriend Joe Pugh, also from Barnsley, suffered shattered knees.

The court heard on the day of the crash, engineers overrode the Smiler's control system without the "knowledge and understanding" to ensure it was safe to do so.

A Health and Safety Executive (HSE) investigation found no fault with the track, the cars, or the control system that keeps the cars apart from each other when the ride is running.

Investigators found the root cause to be a "lack of detailed, robust arrangements for making safety critical decisions" and that the whole system, from training through to fixing faults, was not strong enough to stop a series of errors by staff when working with people on the ride.

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Crews from the West Midlands Ambulance Service rescuing those trapped on the Smiler rollercoaster at Alton Towers Resort West Midlands Ambulance Service

Speaking outside the court, Nick Varney, Chief Executive Officer of Merlin Entertainments plc said: "From the beginning the company has accepted full responsibility for the terrible accident at Alton Towers and has made sincere and heartfelt apologies to those who were injured. I repeat those sentiments here today as we did in court yesterday.

"In accepting responsibility and liability very early on we have tried to make the healing and compensation process as trouble free as possible for all of those involved. We have strived to fulfil our promise to support them in every way and I promise that this support will continue as long as they need it.

"We were always aware that we would end up here today facing a substantial penalty, as has been delivered by the court today. However, Alton Towers - and indeed the wider Merlin Group - are not emotionless corporate entities. They are made up of human beings who care passionately about what they do. In this context, the far greater punishment for all of us is knowing that on this occasion we let people down with devastating consequences.

"It is something we will never forget and it is something we are utterly determined will never be repeated."

Neil Craig, head of operations for HSE in the Midlands said: "People visiting theme parks should be able to enjoy themselves safely. On 2 June last year Merlin Attractions Operations Ltd failed to protect their customers, they badly let them down.

"This avoidable incident happened because Merlin failed to put in place systems to allow engineers to work safely on the ride while it was running. This made it all too easy for a whole series of unchecked mistakes, not just one push of a button, to result in tragic consequences.

"Since the incident Alton Towers have made improvements to the ride and their safety protocols, and the lessons learned have been shared industry wide."

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An air ambulance airlifts one of the patients to hospital after the Smiler crash Getty