The Central Line has been reopened after trains were suspended to and from the Olympic Stadium due to signalling failures.
The suspension has caused major delays on what will be the busiest day of the Olympics so far as the athletics events get under way.
Trains were packed with thousands of commuters and Olympic visitors when the service was suspended between Liverpool Street and Leytonstone. Signals failed at the worst possible time - around 7.40 am - as the morning peak was building and with Games visitors heading for the 10 am start of athletics at the stadium. Trains were halted for an hour.
Service only resumed with severe delays throughout the length of the route Mainline Greater Anglia services into Liverpool Street were also delayed by a broken down train. The Central is one of the busiest on the network and used by more than 650,000 passengers a day.
Passengers were evacuated from stranded trains at stations. There were none stranded in tunnels.
The Central and Jubilee lines are to the two principal routes serving central London with the Stratford.
A Transport for London (TfL) spokesman said: “We have engineer on site and we are working to restore services as quickly as possible.
”We are advising Olympic visitors to Stratford to use other routes - the station is used by nine other lines. They can also use District and Hammersmith & City line services to West Ham station which is only a short walk away.“
Passengers heading into London were advised to use Greater Anglia services instead where the tickets would be accepted.
But there delays there too with Greater Anglia services from Cambridge via Tottenham Hale into Liverpool street suffered delays of 30 minutes due to a broken down train at Cheshunt.
Stansted Express services to and from the airport into Liverpool Street were also disrupted. Delays lasted throughout the peak.
Heathrow mainline rail services - Heathrow Express and Heathrow Connect - to and from Paddington both suffered delays today due to a signal failure.
The signals failed just before 7 am on a stretch of line close to the airport.
Heathrow Connect trains were not running between Hayes and the airport.
Passengers were advised to use the Piccadilly line or other alternative methods of travel.
Tube and mainline passengers were warned trains would be at their busiest today with the start of events at the Stratford Olympic Stadium.
Peter Hendy, the transport commissioner, said: ”Today and Saturday will be the busiest days of the Games so far as the Olympic Stadium opens its doors and sporting events continue to take place across the capital.
“Stratford City Westfield may not be open to shoppers without a ticket during these times but London has a rich and vast array of other attractions to offer during the Games, so I encourage everyone to enjoy the theatres, restaurants, shops, free concerts, Live Sites and attractions and to continue to use GetAheadoftheGames.com to plan your journeys.”
Passengers took to Twitter to express their anger and frustration.
Daniel Laughton summed up the mood; “”Argh! Central line part suspended today of all days.“
JC Tweeted: ”Wouldn't even bother getting on the Central line. About 500 people waiting for tthe same bus at :Leytonstone and I'm cold.“
Andrea Nagel wrote: ”Oh Central line, Central line, Central line. We do love you. But really? Again? Today?“