The Tube strike, which is scheduled to run until Friday morning, began at 6:30 p.m. (1730 UTC) Wednesday, causing disruption for millions of commuters and tourists. Those who were able left work early or canceled happy hour dates to squeeze into stations in order to get home before the strike kicked off.
Talks between management and workers over running trains 24 hours on weekends broke down again Monday. Union leaders want the city to postpone the September 12 expansion until the sides agree on pay and conditions.
Mick Cash, leader of the National Union of Rail, Maritime and Transport workers, called all-night service "rushed and botched from the off."
The Tube handles up to 4 million journeys every day. The first train generally leaves the end of the line at around 5 a.m., with the last rolling in at around midnight. From September, trains will run 24 hours on Friday and Saturday on five of London's 11 Underground lines.
The latest strike comes less than a month after the four main trade unions completely shut down the system for the first time in 13 years. Tube workers also launched a two-day strike in 2014. Recently re-elected Prime Minister David Cameron has made austerity a cornerstone of his policy.
'Not party animals'
London Mayor Boris Johnson said the city had already offered Tube staff a "generous" package that would not see workers taking on more hours than they had at the moment. He also rejected suggestions that the night Tube would only benefit partygoers, saying it would aid the city's many shift workers, who must currently endure lengthy journeys by bus.
"These are not party animals, not just people going home after a night out," Johnson told BBC radio on Wednesday. "They are the working people of London."
The strike caused inconvenience for football fans who had traveled to see English champions Chelsea host Italian side Fiorentina in a friendly game at Stamford Bridge. However, alternative transit services such as Overground trains and buses ran as normal.
"We have made every effort to reach agreement with the unions and avoid this unnecessary strike action," Steve Griffiths, London Underground's chief operating officer, said Wednesday. "On the table is an extremely fair offer."
mkg/cmk (AFP, AP)