Millions of Londoners faced travel misery on Thursday as another strike by Underground staff shut down most of the network, including almost all lines and city centre stations.
The latest industrial action, by members of the Rail, Maritime and Transport (RMT) and Unite unions, follows several prior walkouts this year amid a long-running dispute over job cuts, pensions and working conditions.
It mirrors strife across numerous UK sectors as pay fails to keep up with inflation at the highest level in decades, with the main nurses' union announcing Wednesday that it will stage the first strike in its 106-year history.
Thursday's walkout on the so-called London "tube" network left travellers struggling to catch buses or find alternative ways to get to work in the city of around 9 million people.
TfL said the tube system was "severely disrupted", with limited or no services running, and advised people to avoid trying to use the network.
Reports said many buses were packed to capacity and unable to pick up hordes waiting at numerous stops, while roads were expected to be more congested than usual.
The RMT said a conditional offer to suspend the strike, made at last ditch talks Tuesday with Transport for London (TfL) bosses, failed amid disagreements over planned job cuts and other reforms.
The union -- which has also been spearheading walkouts on the national rail network this year in a separate dispute -- held pickets at numerous stations across London, including at the hub King's Cross.
"TfL have missed a golden opportunity to make progress in these negotiations and avoid strike action," RMT General secretary Mick Lynch said.
"Our members are resolute in their determination to see a just settlement to this dispute, and they will continue their industrial campaign for as long as it takes."
Ahead of the walkout, TfL blamed the RMT and Unite for the stalemate.
"No proposals to change pensions or conditions have been made," TfL's Chief Operating Officer Glynn Barton said in a statement following Tuesday's failed talks.
"Unfortunately, no agreement could be reached but we remain open for discussions."