How many more?

As the nation suffered its sixth fatal train crash in as many years, survivors, passenger groups and industry experts were left wondering, how many more?

Confidence in the network, just beginning to return after the Hatfield and Selby tragedies, was left shattered when a passenger train derailed as it entered Potters Bar station in Hertfordshire.

Witnesses described their terror as one of the carriages hurtled sideways along two platforms.

Last night, Louise Christian, the solicitor acting for the victims of the Southall and Ladbroke Grove disasters, called for an immediate public inquiry into yesterday's tragedy and the Hatfield crash two years ago.

The cause of the crash was not immediately clear, although a set of wheels came off the final carriage, and investigators covered a set of points immediately behind the accident scene with blue tarpaulin.

The four-carriage electric train left the tracks at 100mph as it sped through the station ten minutes after leaving King's Cross en route for King's Lynn.

The final carriage of the 12.45pm West Anglia Great Northern scythed through the station, ending up wedged beneath a canopy.

The front three carriages remained upright and driver Andy Gibson was not injured. There was no guard on board.

The crash also damaged a bridge, raining debris on to traffic passing through the town centre below.

Estate agent Jeremy Birchell, 28, saw the crash from his office, then felt the impact as a huge cloud of smoke was sent flying towards him.

"The train was absolutely hoofing along and some part of it must have been off the rails already because it knocked away parts of the bridge," he said.

"It was going at a tremendous speed and, when it struck, there was a really, really loud noise, and I could feel it as well.

"We could see a person stuck under concrete, she was under there for about 40 minutes and I'm afraid she looked absolutely limp."

Fitness instructor Andy Perversi, of Potters Bar, who was at the station, told how he held a woman of Chinese origin in his arms to comfort her.

"After a while a paramedic came along, but he said there was nothing he could do for her and we should cover her with a blanket."

Transport Secretary Mr Byers said he had asked investigators from the Health and Safety Executive to report their preliminary findings about the cause of the accident to him "as soon as possible".

He said: "It's very difficult in the aftermath of an accident like this to point out that, actually, travel by rail is one of the safest forms of travel in our country."

The crash caused chaos on the East Coast Mainline where operator GNER rerouted services via Hertford, adding about 30 minutes to journey times. A spokesman said travellers should expect short notice cancellations of some services over the weekend.

Ernie Preston, secretary of the North-East Rail Passengers' Committee, said the crash was more "bad news" for the railways. "It is a tragedy and we obviously need to find out how it happened."

John Dunwell, from Aiskew, near Bedale, North Yorkshire, who escaped the Selby crash with only minor injuries, said: "I have been very lucky to come through something like this.

"To hear of it happening again just sends a shiver down your spine.