Rail industry experts yesterday discounted claims by the company responsible for maintaining the points at Potters Bar that sabotage was to blame.
The claims by Jarvis that metallurgists had found evidence that the points had been tampered with were dismissed by one industry expert as ''stuff and nonsense''.
Jarvis's chief operating officer, Ken Hyde, said a ''silvery thread'' had been discovered on one of the bolts, which had fallen off the points, triggering the crash. ''Metal experts told us that was done 24 hours before the accident,'' he said.
However, senior engineers close to the official investigation team have told the Independent on Sunday that Jarvis's claims have little foundation. More than 100 trains had passed safely over the points in the 24 hours before the accident.
Many were high speed trains heading for the North- East and Scotland, as well as fast Home Counties trains, such as the 12.45 to King's Lynn, which came off the rails. But 41 trains were slow suburban services, most of which were switched across the points into the northbound stopping platform with no problems.
The last train to be switched safely across across the points on the day of the accident was the 11.36 King's Cross to Peterborough, which stopped at Potters Bar at 11.51. An indicator in the signal box at King's Cross registered electronically that the points switched properly. Minutes later, the points switched incorrectly under the fourth carriage of the 11.45 from King's Cross, leading to the death of seven people.
Experts said last night that this sequence of events was far more likely to indicate bad maintenance than sabotage, which would have derailed a train much sooner. A British Transport Police spokesman said that Jarvis had had access to only "secondary" photographic evidence, rather than the primary evidence under investigation.
Jarvis's claims were also dismissed by the rail analyst Christian Wolmar. He said in an interview on BBC radio yesterday it was in the company's interests, because of its falling share price, to identify factors other than maintenance as the cause. "It is a company flailing about," Mr Wolmar said.
Mr Wolmar said his own sources suggested that the crash was ''down to some odd attempt at maintenance – it was a cockeyed bit of work. The points were out of alignment."
British Transport Police also ruled out any connection between the arrest of two men on the rail line at Stevenage, some 20 miles down the line, and the crash.
The cross-party Commons select committee on transport is to put further pressure on Stephen Byers, the Transport Secretary, by warning that he is running out of money for improvements to the rail network.
The report on the Government's 10-year transport plan will show that only about £5bn is left of the £60bn allocated to rail.
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