Boxing Day Tube services disrupted by drivers' strike
A number of London Underground drivers have gone on strike in a long-running row over bank holiday pay.
Large parts of the service have been disrupted as a result of the Boxing Day strike and more buses were brought in.
Members of the Aslef union have walked out for 24 hours from after voting 9-1 in favour of strike action.
Transport for London (TfL) said limited services were expected to be reduced further after 21:00 GMT, with few or no services on most lines.
It urged passengers to check before travelling. There are no services on London Overground.
TfL said the Bakerloo, Central and Victoria lines were running services through central London during the day.
The District, Hammersmith & City, Circle, Metropolitan, Northern and Jubilee lines have been running limited services.
The Piccadilly line is operating a shuttle service between Heathrow terminals and Hammersmith, and between Arnos Grove and Cockfosters.
The Docklands Light Railway has also been operating, except between Canning Town and Beckton and between Shadwell and Bank.
TfL said services would vary throughout the day depending on the resources available.
Extra buses have been laid on for shoppers heading for the West End and for the Westfield shopping centres in east and west London.
Otherwise, the capital's 700 bus routes have been operating a Sunday service.
The congestion charge for vehicles entering central London does not apply during the festive period and there are no on-street parking charges in Westminster.
It is the third successive walkout by Tube drivers on what is the first day of the post-Christmas sales.
An Aslef spokesman said: "For three years on the run, our members have voted by over 90% to take industrial action on Boxing Day.
"There is clearly a major problem. But London Underground refuses to deal with it - or even treat it seriously.
"Last year they said they would begin talks 'in the first quarter of the year'.
"They did not open discussions until a few weeks ago. And at those discussions they offered precisely nothing."
Howard Collins, London Underground's chief operating officer, criticised the union for demanding to be paid "twice for the same work".
"The scandalous actions of the Aslef leadership are an attempt to hold Londoners to ransom, and demonstrate a wholesale disregard for our customers," he said.
"We will be running as many services as possible, supported by London's 700 bus routes, but there will be disruption."
The disruption, which led to the Premier League derby between Arsenal and West Ham United being postponed, is due to continue with two further walkouts on the last two Fridays in January.