It is significant that both the Potters Bar and Lambrigg derailments took place on facing points that were not regularly used.
The components cope with normal vibration. In the days of British Rail if a routine visual inspection of the points showed just one bolt broken or stretcher bar or fixing lug cracked, or the nuts were found to be regularly slack, then vibration would be deemed too great. Action would be taken as soon as possible on the packing of the ballast beneath.
An inspection was not carried out at Potters Bar immediately prior to the crash, despite reports the night before of a ride so bad as to be 'almost lethal' in the vicinity. Lifting the points out and taking them to Buxton destroyed any evidence of the state of the packing.
From the 19th century the use of facing points has been frowned on unless absolutely necessary and mechanical signalling crossovers were laid trailing.
Valuable maintenance knowledge and experience seems to have been lost during the Railtrack era, and health and safety now makes it more difficult to inspect points, let alone repack the ballast.
It seems from the Grayrigg accident, as at Potters Bar, that it has become acceptable to just keep tightening the nuts.
Richard Chown (M) Woodlawn, Philpstoun, West Lothian EH49 6RH