A “complete loss” of signalling on part of South West Trains' London service caused severe disruption for late-night travellers.
Trains were halted for around four hours last night between Waterloo and Clapham, forcing many passengers to find alternative ways home from the capital.
Customers were urged not to travel through Waterloo when the signalling was lost at around 8pm, with one passenger describing it as "chaos".
Engineers managed to get the service up and running shortly after midnight, but not before many passengers had taken to social media site Twitter to vent their frustration.
Lucy Blair tweeted shortly after midnight: "Over 3 and a 1/2 hours to get home. Congratulations to South West Trains on hitting a new all time low."
Another, Andre Dang, said at 11.30pm last night: "Thanks to South West trains, I've only just got home. And even that was with the help of a lift. Waterloo was chaos."
A spokesman for the South West Trains-Network Rail Alliance said: "The signalling problem between London Waterloo and Clapham Junction has been resolved and trains are now running in and out of London Waterloo.
"We would like to apologise to customers for the disruption to their services.
"We expect to operate a normal timetable to operate today, although some trains may be shorter than usual and passengers are advised to check the latest updates before they travel."
Passengers who were unable to use their tickets were told they would be able to use them today, or make a claim to have them refunded along with any incurred travel costs.