'There was lots of blood, and people on tracks with limbs twisted where they shouldn't be'

Bodies strewn across railway tracks, a derailed carriage screeching down two platforms as passengers ran for their lives and City commuters, bloodied and shocked, carrying their briefcases and holding cracked heads, walking in a daze through the wreckage.

Bodies strewn across railway tracks, a derailed carriage screeching down two platforms as passengers ran for their lives and City commuters, bloodied and shocked, carrying their briefcases and holding cracked heads, walking in a daze through the wreckage.

This was the scene at Potters Bar shortly after 1pm yesterday and, as the dust settled and the death toll mounted, the words on everyone's lips were: "Not again". Less than two years ago, down the road in Hatfield, they were saying exactly the same thing.

The 12.45pm from King's Cross to King's Lynn in Norfolk, a four-carriage "Cambridge Cruiser", was hurtling along at between 70 and 100mph. Some 150 people were thought to have been on board, many of whom would have escaped work early to enjoy the weekend with their families.

According to the driver, Andy Gibson, who escaped uninjured, it had been a normal journey until just south of Potters Bar station when, as he later told officials at Aslef, the train drivers' union, he felt something give in the carriages behind him.

The fourth carriage of the train came off the rails, hit the iron railings and brick skirt of a road bridge it was crossing and skewed round so it was sliding on its side at 90 degrees to the track. It mounted at least two platforms and screeched its way along towards some 25 waiting passengers before coming to a halt, leaning at 45 degrees, wedged under the platform roofs. Only the roof supports killed its momentum, otherwise it would have crushed the waiting passengers.

"I heard a loud bang and a lot of crashing and the train was coming along and I ran away," said Sam Irvine, who was on platform one. "It almost hit me. Then we jumped down on to the track. There were five or six people lying on the track. They had been flung from the train. We covered people with our coats and tried to get the debris from on top of them. Some people on the tracks were dead, two or three. Then a woman who I and another man were trying to help just died in our arms."

That other man was Andy Perversi, 21, from Potters Bar. He said: "After she died, we smashed windows to help people get out. There was panic and a lot of screaming. It was chaos. There were people on the tracks with limbs twisted where they shouldn't be, and there was a lot of blood.

"There were people on the tracks in suits and with briefcases, just holding their heads and covered in blood. It was horrible."

Ajay Thakariya, a 20-year-old student, was watching a London-bound train pull in when he heard a loud bang behind him. "I looked around and saw the rear end of the train flip over and swing around and it started coming towards us along the platform," he said. "There were about 10 of us and we just ran. I was probably the closest and I was about 20ft away when I turned round and it had come to a stop.

"I saw about six or seven bodies outside the train. The waiting room on the platform was totally crushed but I don't think there was anyone in there."

Underneath the bridge damaged in the accident, motorists also found themselves in the middle of a nightmare.

Ron Tarling, 71, was being driven by his wife, Gill, to a family celebration when the train ploughed into the station above. He said: "I just couldn't understand what was happening at first. We were stuck in traffic just under the bridge when there was a loud crash and all this debris, masonry and steel, just began falling all over the car. It just kept raining down on us.

"I put my hands over my head. I was convinced we'd had it. When it stopped, our car, a Vauxhall Corsa, was wrecked. I can't believe we managed to get out alive. We're very lucky indeed." He escaped with a minor cut to his head.

The accident could have been much worse. Only two hours later, the platforms would have been swarming with children from the nearby Dame Alice Owen school. "Our main concern is the children at the moment," said a member of staff. "But yes, we are aware we should count our blessings."

Alan Heath, the boss of a decorating company 100 yards from the crash site, heard the impact and ran to help. He passed ladders over a metal fence to firefighters before climbing on to the track to help.

He said: "I saw three people on the track; they were dead. And there were still some people inside the carriages. The firemen were trying to get someone out on a stretcher, feet first, but they had to give up because she was a bit more seriously injured than they thought. I couldn't see what was holding the carriage up. It was unsupported and leaning over at 45 degrees."

He and colleagues collected debris along the platform and used metal bars to prevent the train from toppling over on to the injured.

Jayne Francis, a cafe owner, told how she helped a young woman in shock. The woman had been covered in dust and debris as the train passed above her as she was climbing a ramp up to the platform.

"She was shocked but unhurt," said Mrs Francis. "She was also very lucky."

Chief Superintendent Andy Wright, of Hertfordshire Police, said: "We have not confirmed the cause of the accident. This a joint recovery process between Hertfordshire Police and British Transport Police and we will be helped by the Health and Safety Executive and the rail industry. As far as we know the injured were all passengers on the train, but we are not able to confirm that. As the train came through the station it came to a sudden halt. The rear carriage is still lodged on the station and the rest of the train is about 400 to 500 yards north of that.

"The rear carriage is on the rails across two platforms and is lodged between two canop-ies. There were no other trains involved. All the emergency services were on the scene within three to four minutes of the accident happening.

"This is the same line as the Hatfield accident around 18 months ago. I was present at Hatfield and it is comparable to that. It's a tragic and very serious incident."

Mark Guest, 29, from Littleport, near Ely, was a passenger in the derailed last carriage and had caught an earlier service than normal because of a dental appointment.

"I remember falling and then hearing a loud bang and I felt the train coming off the tracks and then I just started rolling," he said.

Mr Guest, who works as a telecoms engineer in London, said he was able to walk away from the crash and used his knowledge of first aid, which he learned during eight years in the army as a full corporal, to help others injured in the crash.

Asked what he thought of another tragedy on Britain's railways, he said: "I just think, why has this been allowed to happen again?"