Points to ponder

TOM UTLEY (Mail) asks why, when computers make it possible to perform keyhole surgery in Kuala Lumpur from a desk in Aberdeen, no one can change a signal on the line from West Croydon to Victoria.

As a former main- line signaller, I can tell him the answer is litter. Signalling operates via small electrical currents sent through the track. Litter blown between the points breaks the circuit. Someone has to clear this up, so the points and signals can operate again.

PAUL CLEGHORN, Bridlington, E. Yorks.