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Deadly trap at Potters Bar

01 Jun 2002

MYSTERY surrounds the derailment of the 12.45 from London King's Cross to King's Lynn on May 10. Approaching Potters Bar at about 160 km/h on the Down Fast track, the last car of the four-car EMU left the rails on facing points. It quickly became evident that the points had moved under the train, directing the final bogie through a 50 km/h crossover towards the Down Slow line. The rear car spun through 90í, shed its errant rear bogie, thundered sideways across upstanding girders of a road underbridge, and wedged itself under the concrete awnings on the two island platforms. Although the aluminium-bodied car survived remarkably well, six passengers and a lady walking under the bridge died.

An interim report issued by the Health & Safety Executive on May 14 focused firmly on the mechanical condition of the points, which are maintained by Jarvis Rail under contract to Railtrack. When these were examined, three very peculiar faults were discovered.

The two switch rails were linked by three stretchers. The first joined the blade ends and carried rods for detection and locking. The second stretcher carried the drive from the motor, and in turn drove the third through cranks and rodding. But the main and locking nuts had been removed (and placed to one side) from one end of each of these drive stretchers, so that they no longer joined the switch rails. It was concluded that the points had been functioning and detecting normally until the higher forces through the locking stretcher caused it to break under the train, leaving the diverging switch rail free to move.

The third fault was extraordinary. Someone had very recently wound nuts inside the rails on the third stretcher through 10 complete rotations, leaving bright steel thread exposed. This forced the diverging switch rail towards the stock rail, closing up the flangeway from 50mm to about 25mm, so it would be hit by passing wheels.

Jarvis says its staff checked the locking on May 1, and a visual inspection on May 9 found no faults. Despite this, HSE reported 'no evidence so far to support speculation in the press about vandalism or deliberate damage' although 'it could not be ruled out'. Off the record, it was telling journalists that the chance of this being the cause was 'less than 1%'.

With its reputation at stake, Jarvis went public with its own findings. Chief Operating Officer Kevin Hyde told us on May 21 'we keep coming to one conclusion: that the nuts had been moved by an unauthorised, informed person. As railwaymen, that concerns us.'