Inside the car sat the driver. He was making no effort to escape

Just after 6pm on Saturday, an off-duty police officer was driving on a small country road close to Ufton Nervet in Berkshire. It was a typical November evening, dark and drizzling.

Just after 6pm on Saturday, an off-duty police officer was driving on a small country road close to Ufton Nervet in Berkshire. It was a typical November evening, dark and drizzling.

As he approached the main London to Plymouth railway line, he noticed the warning lights on a level crossing were flashing. The barrier had come down to stop traffic.

Through the gloom, he noticed a car across the railway line. There was little doubt it had been parked there and, inside, was the driver, making no attempt to move the vehicle or to flee.

As he watched with mounting horror, the 5.35pm Paddington to Plymouth express, which had left Reading six minutes earlier, passed a green light and was bearing down on the crossing at about 100mph.

The police officer, as yet unnamed, jumped out of his car and ran to the emergency phone at the side of the barrier.

As he must have feared, it was much too late. Within seconds ­ and before he could get a response ­ the First Great Western express train sliced through the saloon car, killing its driver instantly, taking the wreckage of the vehicle with it.

There were reports that the train driver had to be dug from the wreckage after his locomotive unit overturned, filling the cab with earth.

The officer dialled the emergency services on his mobile immediately. It was 6.10pm.

As one of his senior colleagues said: "He was an experienced officer and he would have seen some pretty dreadful sights. Nothing would have prepared him for that."

After hitting the car, the train careered on for nearly 100 yards, derailing as it went and spreading debris over the adjoining fields. Finally, it shuddered to a halt, the train driver and five passengers, including an eight-year-old girl, dead or dying.

Speculation was growing last night that the driver of the car may have intentionally parked on the tracks as a police spokeswoman said investigating officers had not ruled out the possibility that he was attempting to commit suicide.

It is thought that the whole train was derailed because it encountered a set of points after the impact which diverted it into a siding where there is a 25mph speed limit. Usually, when a train hits a car, the vehicle is crushed and brushed aside, and most of the rolling stock stays on the track.

Although passengers on the train said they thought the driver had applied the brakes, there was no chance of it stopping before the crash. At 100mph, it takes about a mile for a high-speed train to come to a halt.

As the derailed carriages ground to a halt, panic ensued.

"At first, it just went all black," said Mario Iotti, a passenger in one of the carriages that turned on to its side. "Some other passengers were trying to calm people down in the carriage. Two guys in my car managed to get the hammers and break out of the top windows. I managed to get out through the door at the back.

"Inside the carriage, there was glass everywhere. Some girls in front of me had their faces covered in blood."

Many passengers used the light from mobile phones to find their way through the darkness. Jon Stace, 21, a graphic design student from London, said: "I thought I was going to die. We couldn't see anything and all I felt was my body being dragged outside the window."

Jonny Saunders, who works for BBC Radio Five Live, said: "We came to a juddering halt and suddenly the lights went off, screaming, shouting and it went pitch black, then total chaos in the carriage for a few moments."

One of the first people to reach the scene was Mark Penston, who was driving home with his two children when he pulled up at the level crossing behind the off-duty policeman's car.

Mr Penston said: "There was a body by the level crossing. I think it was out of the car. I didn't really want our kids to see it.

"The thing that struck me initially was the silence, no one crying, screaming or shouting. It was total darkness apart from light sticks. People were absolutely confused and no one knew what had happened. There were people wandering about.

"The magnitude of the destruction struck me. I have never seen anything like that before. Every carriage had been derailed."

While many passengers were trapped in the overturned carriages, others managed to clamber out of the wreckage.

More than 20 ambulances and 14 fire engines arrived at the scene and walking wounded were taken to the Winning Hand pub in Ufton Nervet, where emergency services set up a temporary first aid post.

As the rescue operation got fully under way, 61 injured passengers were taken to Royal Berkshire Hospital in Reading, while medical staff began the task of removing bodies from the wreckage.

The death toll reached seven yesterday after a man who was in critical condition in hospital died. None of those killed has been named but the train driver is believed to have been based in Exeter.

The scene left by the crash was one of devastation. As dawn broke through the autumn drizzle yesterday, a mangled zig-zag of carriages could be seen strewn along the track.

The casualty list could have been considerably longer. Unusually, the relatively empty first-class carriages were at the front of the train, where packed second-class coaches would have normally have been. It was not clear last night why the service was assembled in reverse order.

The service was carrying about 300 passengers and most observers thought it was a miracle that more people were not killed. The train had stopped at Reading and was on its way to Newbury, its next stop. It was due to call at Pewsey, Westbury, Castle Cary, Taunton, Tiverton, Exeter, Newton Abbot and Totnes, before arriving in Plymouth at 21.14.

As darkness fell last night, the work of pathologists was completed to allow police to remove the last two of the four corpses that had been unrecoverable the night before. Scenes of crimes officers carried out checks on the train, the crossing and the crash car. A police exclusion zone forced the closure of part of the busy A4 running parallel to the railway line and prevented the public from coming within a mile of the crash site.

A police helicopter took pictures overhead which will be used to analyse the cause of the crash. For the public, all that was visible in the gloom was a trackside arc light and a crane moved into place for today's task of removing the train.

At the level crossing, the red lights warning of an imminent train were stuck in flashing mode and provided a sobering scene. A sign warned drivers of large or heavy vehicles to telephone ahead for permission to cross.

Last night, as more than 100 police officers, firefighters and forensic scientists continued to scour the tracks for clues, a bunch of maroon and pink tulips wrapped in purple paper was placed next to the level crossing. The flowers rested beside the yellow emergency phone used by the off-duty police officer when he tried in vain to avert the tragedy, a memorial to the latest disaster to hit Britain's railway network.

The difference with the ill-fated 5.35 from Paddington may turn out to be that this crash, unlike several others, was largely unavoidable.