The owners of one of Britain's largest theme parks have been ordered to pay £100,000 after a ride broke loose and left two teenagers dangling dangerously in the air.

Home video footage of the children screaming as their ride came adrift was shown in court yesterday.

They were on the Zodiac Enterprise ride, a 40ft diameter big wheel with 20 gondolas at Thorpe Park near Chertsey, Surrey, when a support snapped.

It was left hanging from one support and, as the operator tried to stop it, the gondola repeatedly hit decking before finally coming to a halt.

The children, then aged 14 and 15 and from St Leonards, were helped to safety but escaped with non-life threatening head injuries, whiplash, bruising and shock.

A judge said it was a miracle nobody was seriously hurt or killed.

Tussauds Theme Parks Ltd, owners of Thorpe Park, admitted failing to discharge its duty of health and safety.

At Guildford Crown Court yesterday it was fined £65,000 and ordered to pay £35,000 costs following the incident on September 22, 2001.

Judge John Crocker criticised procedures after hearing that strange noises had been identified when the ride opened in the morning.

However, it remained open against manufacturers' advice for more than six hours, by which time hundreds of people had been on board.

Judge Crocker said: "It is a miracle in my view that this didn't turn into an absolute tragedy. Thankfully, the two young people received only minor injuries, although it must have been an absolutely terrifying experience for both of them."

The two children were on a school trip when they decided to go on the Enterprise ride, described as "not for the faint-hearted".

Nicholas Wood, prosecuting, said: "They were entrusting themselves to the proprietors of Thorpe Park. They were going there for entertainment and enjoyment on rides that were designed to thrill.

"Unless maintained and operated correctly at all times, they are exposing people to risk."

On the day of the accident, the operator heard a clunking noise after it was opened at 10am and reported it to her team leader.

He in turn said he would report it to the maintenance engineers to inspect it.

But it was not until 4.20pm - six hours after the first noise was heard - that two engineers attended.

Mr Wood said they could not immediately diagnose the problem so one of them decided to travel on the ride.

He added: "While he was engaged in that and as the ride was at its high point, he described there being a huge bang and the whole ride shook.

"He said the gondola with the two children inside dislodged and then hung loose."

The accident was reported to the Health and Safety Executive (HSE), which launched an investigation. Officials found stress corrosion on one of the bolts, which had fractured and failed.

Adrian Mahon, corporate affairs director for the Tussauds Group, told the court drastic changes had been made to engineering procedures since the accident.

A committee was now in place to deal with health and safety at the group's three theme parks - Thorpe Park, Chessington World of Adventures and Alton Towers.

Andrew Hogarth, QC, defending the Tussauds Group, said the two children were sent a letter of apology shortly afterwards.

It was the first time anyone had been injured because of mechanical failure on any of their rides in the six years since Tussauds Group bought the attractions.

Mr Hogarth said newly-introduced safety procedures meant that if any untoward noise was heard on the Zodiac Enterprise ride it was immediately shut down.

He said: "Although the systems in place were not good enough, this was not a dereliction of duty of any significance.

"The defendant has taken considerable steps to ensure that this incident, which is very rare, will not occur in the future."

Two managers - Christopher Edge, 47 and Keith Workman, 46 - were charged with an identical offence but cleared when the Crown dropped the case three days into their trial at Woking in January.

Outside court, Russell Adfield, principal inspector for the HSE, said: "It was a serious incident resulting from a breakdown in communications and management procedure.

"The ride should have been stopped before that car detached.

"Failure to properly maintain safety at fairgrounds is unacceptable and this prosecution and fine reinforces that message."

Following the case, Thorpe Park issued a statement reaffirming the company's commitment to health and safety.

It said: "Thorpe Park delivers more than 14 million rides to guests every season without incident and has an excellent safety record. The park is totally committed to the health and safety of its guests and the quality of all its operations."