A fresh 24-hour Tube strike is due to start from 18:30 BST following the failure of talks to resolve a dispute between unions and London Underground.
All stations are expected to close, with the four main Tube workers’ unions supporting the industrial action.
Drivers are unhappy at pay and conditions offered for working on the new night service.
London Underground (LU) apologised for the disruption, saying the latest offer aimed at improving work-life balance.
Mayor Boris Johnson called the offer “incredibly generous”, said he would not authorise any more money being added to it, and said he was “not fussed” about the night service starting on September 12 as planned, as long as it started in the autumn.
One official from the Rail, Maritime and Transport union (RMT), told BBC London members would “escalate action” in the run-up to the scheduled start of the night Tube service.
The latest strike will be the second time Tube stations across the capital have closed in the current dispute, following a 24-hour walkout on July 8-9.
Services was experted to stop running from 18:30 BST yesterday and there will be no trains on today. Transport for London (TfL) advised commuters to complete their journeys before the action began. –BBC
Some 250 extra buses will be laid on during the strike, extra river services will also run during peak hours and extra cycle hire hubs will be added in some areas, TfL said.
LU said the new offer included a 2% salary increase this year, an extra £200 per night shift for drivers for a limited time and a £500 bonus for night Tube staff when the service is introduced in September.
Aslef, the RMT and the Transport Salaried Staffs Association (TSSA) have all turned down the offer.
Unite previously said its action “would go ahead”.