This is the horrifying moment The Smiler crashed at Alton Towers, injuring 16 people, including two young women who later had legs amputated.
The grainy CCTV clip of Britain's worst rollercoaster crash in years shows the ride smashing into an empty carriage with the same force as a 90mph (145kmh) car crash.
The footage, published for the first time today, shows the Smiler stop at the top of a loop before bungling Alton Towers engineers overrode a system warning and sent it headlong into another truck on June 2 last year.
The carriages collided so hard the two meshed together, crushing the limbs of people in the front row and sending the ride swinging back-and-forth like a pendulum.
At least 16 people were injured, five seriously, when the rollercoaster smashed into a broken-down carriage after a series of blunders.
Victims who lost limbs, broke bones and suffered internal injuries in the disaster relived their ordeal as they faced the theme park's bosses at Stafford Crown Court yesterday in the sentencing phase of the trial.
Merlin Attractions Operations Ltd, which owns and operates the Alton Towers theme park, previously admitted a breach of health and safety rules over the accident.
Merlin faces a multi-million pound fine and potentially millions more in compensation claims from the victims following a Health and Safety Executive prosecution.
Leah Washington, 18, from Barnsley, South Yorkshire, and Vicky Balch, 20, from Leyland, Lancashire, each had a leg amputated as a result of the horror crash.
Staff, under pressure to keep the ride in almost constant use and offered bonuses to keep it running, had not even read the manual for the £18m rollercoaster.
Engineers then overrode a fault detected by the computer system and sent the ride crashing into an empty carriage with the force of a "90mph car crash".
The court also heard engineers should have seen the empty carriage, which was visible on CCTV cameras covering the track.
Prosecutors revealed the weather should have shut down the ride and engineers were ill-equipped to deal with the aftermath.
The court heard:
• Victims were "suspended [in mid air] for several hours" and suffered "very significant blood loss" leading to loss of limbs
• Impact of packed ride smashing into an empty carriage equivalent to "a family car of 1.5 tons having collided at about 90mph"
• There were "near gale" winds of 46mph on day of crash - but Smiler should not run at more than 34mph. Other rides at Alton Towers were shut down.
• None of the rollercoaster's four key engineers "had the full picture or understanding of conditions on the ride" - and may not have all read the instruction manual
• One had overridden a computer system "block-stop", believing it had halted the ride in error, sending a full 16-seater rollercoaster car around the track and into the empty carriage.
• Judge says disaster aggravated by difficulties emergency services had getting to victims left in mangled ride for almost four hours
Nicholas Varney, 53, chief executive of Merlin Entertainments, and Alton Towers divisional director Ian Crabbe attended court.
The court heard Varney, a father-of-four, took home a £733,000 pay packet in the same year as the Smiler crash.
Speaking on their behalf, Simon Antrobus, defending, said: "They wish me to deliver an apology to the court and to those injured and affected by this ride."
Judge Michael Chambers QC, the Recorder of Stafford, asked: "Has anyone resigned as a result of the incident?"
Antrobus conferrred with Varney before replying: "No."
The trapped riders had to wait more than four hours to be freed from the crumpled carriage while rescue workers battled to reach them as they sat 25ft (7.5m) up in the air at an angle of about 45 degrees, pinned in by the mangled metal.
But the company has been criticised for putting profits over people and keeping the ride open even after appalling injuries sustained on it.
Opening the case, barrister Bernard Thorogood said the kinetic energy involved in the crash was equivalent to "a family car of 1.5 tons having collided at about 90mph".
He said a test carriage had been sent around the 14-loop ride, but had failed - known as 'valley-ing' - in the bottom of the Cobra Roll area of the ride, unseen by ride staff.
The engineers had re-set the ride and overridden a computer system "block-stop", which they believed had halted the ride in error, sending a full 16-seater rollercoaster car around the track and into the empty carriage.
Thorogood added: "The subsequent collision was plain to see to some in the train, and I refer to those in the front row's statements, where they speak of their disbelief and horror as they saw ahead up the track the train into which there were going to dive."
The barrister, speaking for the Health and Safety Executive (HSE), which brought the prosecution, said: "Engineers who came to remedy the situation, regarding the indicated block-stop, thought it was a false one reflecting a recently corrected issue and did not see the stalled train, and proceeded to re-set and re-start the ride, overriding the computer-generated block-stop."
However, he added that although there had been "a number of human errors", the "fault here is with the employers", and not individuals.
Thorogood said engineers, responding to a fault, were "without guidance from above", and had not been given a system to follow to safely deal with the problem on the track.
He added: "The fault is with the defendant for not devising a scheme for not guiding the work of the engineers."
Judge Chambers will hear evidence of the HSE's investigation into the crash, and mitigation from Merlin, before passing sentence.
At the beginning of Monday's hearing, Judge Chambers said: "One of the features is not just the impact on those injured, but on those close to them."
He added that he had read all the victim impact statements.
He said the wounds suffered, both physical and psychological, had "changed the lives of the some of those injured, in the most dramatic way".
In its investigation, the safety watchdog found that a "near-gale" may have been to blame for the empty carriage failing to clear the Cobra Loop in the first place, following an early problem with one of the ride's lifts.
Thorogood said: 'One first empty train was sent to establish the lift was operating normally but, unknown to those present, this train failed to clear the loop - with which this case is unfortunately and sadly concerned.
"The problem was that the head-wind which that train could not overcome."
The Smiler ride itself, it was concluded, was "well-designed" as were the computer and "sophisticated" control systems, and the operator of the ride had followed safe working practices.
It concluded that the defendant, Merlin, fell "far short" when it came to governing the inevitable need for engineers from the park's technical service's department to fix faults on the ride.
However, he added that there was "absolutely no evidence of a task analysis-based approach for engineering work, in particular in dealing with ride faults".
Thorogood, summing up that point, said "engineers revealed a range of understandings to important aspects, which with a single system [of working] there would not be".
As an example, Thorogood said one engineer who worked on the Smiler that day told investigators after the crash that he had "assumed" the rollercoaster had been fitted with a type of safety trip-switch present on at least one other park ride, when in fact it had not.
The court was told the victims of the Smiler crash were held at a "very difficult angle" as the two trains on the ride "meshed together".
The prosecution went on to say that none of the four engineers involved in working on the Smiler 'had the full picture or understanding of conditions on the ride'.
'There was no single member of technical service staff in control,' Thorogood said.
He added that there were "various states of knowledge" of the fault alarm systems on the ride.
He said: "The staff had come to distrust at that stage the fault signal on occasions and hence they thought that the one that was showing was an error.
"There was nobody, no individual who had to sign off and take responsibility for that event.
"A number of errors were made. The defendant is ultimately responsible for these errors though they were made by individuals."
The Smiler reopened in March this year with 'improved safety measures' but student Miss Balch said she hoped the ride would 'be destroyed'.
A court hearing in April this year was told Merlin had conducted an internal investigation following the incident, which established that a worker manually "overrode" the ride's governing computer system.
Indicating a guilty plea to breaching the Health and Safety at Work Act, Merlin's barrister told the previous hearing that the company accepted additional measures could have been taken to guard against safety risks.
Lawyers for the Health and Safety Executive (HSE) have said the 1.1km Smiler, which opened in 2013, never had "a proper settled system" for staff to follow when carriages stopped on-track.