Brian Mellitt, the director of engineering, sent a fax to the operators of seven other ageing metro systems including New York, Paris, Tokyo and Sydney, in an effort to find out whether they have encountered the same problem which has caused the disruption.
Yesterday, attempts to run empty trains on the system were successful for four hours until an eighth train was introduced and the system blew again. Mr Mellitt said: 'We still do not know where the fault is. We think it is in the Mile End area but we are not sure.'
The problem, which according to Underground engineers is unprecedented, is the intermittent nature of the failure, which is in part of the 22,000- volt cabling which delivers the main power around the network. The fault only occurs after the system has been operating for a while and then seems to be so minor that it repairs itself, making it untraceable.
Passengers yesterday were able to make use of a fleet of 80 buses but many workers stayed away or used other transport.Reuse content