Commuters face an evening of misery and upheaval as the problems on the Central line continued throughout the day.
Despite assurances that the line would return to normal by lunchtime, disruption will run into the evening rush-hour.
The track was closed after the derailment of an engineering train at Holland Park overnight. But just 20 minutes after the line was re-opened another part of the line between Holborn and Leytonstone was closed again with reports of a person under a train.
The Central line is a key route to east London and covers major central London stops such as Tottenham Court Road and Oxford Circus.
In the morning, the delays had led to the closure of stations with reports of a 45 minute journey taking three hours. Again, this was compounded by unseasonally warm temperatures which led to uncomfortable journeys on alternative rammed routes.
It was the second successive day of disruption on the Underground. Three Tube lines, including the Jubilee line, suffered delays in the morning rush-hour yesterday and there have been a number of other mornings lately when services have been disrupted.
Mick Cash, general secretary of the RMT transport union, said: “Our officials are seeking to obtain further information on the serious derailment last night.
“While the union seeks to establish the facts, the incident once again throws under the spotlight the ever present issue of safety on the Underground for both staff and passengers alike.”
Early in the day there had been severe delays for a time on the Hammersmith & City line due to a signal failure at Plaistow while in the afternoon a signalling problem at South Acton led to a part-suspension of London Overground between Willesden Junction and Richmond.
5.30pm update: TfL is now reporting only minor delays due to an earlier customer incident and an earlier derailed engineers train at Holland Park.