At the height of the chaos, 29 trains were stuck in tunnels on the District, Metropolitan, Circle, East London and Central lines. The Northern Line was also affected. In addition, the radio network was put out of action, which delayed evacuation and some people were not brought out until almost midday.
Last night, London Underground said services east of Liverpool Street on the Central Line would be cancelled today for repair work to be carried out after the problem was traced to a trackside cable in the Hainault loop of the line. Buses are to run from Hainault, Newbury park, Epping and Woodford stations.
The chain of events began on Tuesday morning, when services on four lines were disrupted for an hour by loss of power. The emergency cable system was brought into action and on Tuesday night engineers thought they had restored services.
However, as soon as the rush hour got under way yesterday, power failed on six lines at 7.10am. It was restored using the emergency cable but at 8am it failed again, plunging large sections of the system into darkness. London Underground estimated that up to half a million journeys were affected.
Sections of the Central Line were hit by a further power failure at about 5.30pm, which brought rush- hour trains to a standstill.
With the bulk of Underground services into the City suspended for half the day, commuters tried to find space on packed buses, but many were forced to walk. By the middle of the morning, the main roads into central London from the east were gridlocked.