The strike is by 7,500 members of the National Union of Rail, Maritime and Transport workers (RMT), who claim safety will be compromised and jobs affected under the controversial government plans to run the tube by a public-private partnership (PPP).
London Underground, on the other hand, claims the strike is unnecessary and has branded the union "impossible" to negotiate with.
What is the effect of the strike?
Those striking include signal workers and station staff who walked out at 8pm last night, leading to travel chaos across the capital.
The strike caused a virtual wipeout of tube trains in central London during this morning's rush hour. Until 8am, fewer than 30 of the usual 500 trains were running, and there were no services at all on many lines in the centre of the capital. This, inevitably, led to overcrowding on overland trains and buses.
The strike is scheduled to end at 8pm tonight, but problems are anticipated throughout the evening. Although members of the train drivers' union, Aslef, were not involved in today's action, many were expected to refuse to cross RMT picket lines, thus adding to the disruption.
How will the dispute be resolved?
A high-court battle to settle the tube funding and management row is looking increasingly likely. Last night it emerged that, were a case to be brought, it would probably begin just days ahead of the possible May 3 general election.
A meeting on Thursday, billed as the "final meeting", between the London transport commissioner, Bob Kiley, and the deputy prime minister, John Prescott, failed to produce an agreement. Both sides have accused each other of reneging on agreements.
Lawyers for Transport for London (TfL), the capital's transport authority, are attempting to declare PPP illegal while the government seems determined to push it through.
Unless a last-minute deal centred on unified management control (which will not see the break up of tube services, maintenance and infrastructure) is agreed, the court action will go ahead, a TfL spokesmen said.
TfL lawyers believe that "there is scope" for a judicial review hearing to begin on or around April 30 and lawyers will argue that the government's plan risks human safety and is too expensive.
Has the fight begun to get dirty?
Yes. Mr Kiley has been playing the safety card and the government have now responded by questioning his own safety record, claiming that, when he finished as controller of the New York subway, its safety record was 40 times worse than the tube's. Furthermore, according to RMT, London Underground is preparing to sue them and to pursue criminal damages against individual activists.
Has there been any progress on this saga?
Not really, no. Tony Blair has closed ranks with John Prescott and Gordon Brown in their determination to force Mr Livingstone and Mr Kiley to "knuckle down" and work within the government's £15bn blueprint for modernising London's underground system. They argue that PPP should have started almost a year ago.
What is PPP?
It is the Treasury's concoction of a public-private partnership that would split the tube into four sections. Three of these would be run by the private sector on 30-year leases. Only one of the sections - the actual running of the trains and signals - would stay in the public sphere. The private sector would raise the funds and be reimbursed by the users of the lines, London Underground and the government.
What are the objections to PPP?
Mr Kiley, an American who has had success in rejuvenating similar underground networks in New York and Boston, has said that the proposed split responsibility is unsafe and that a "unified management" is crucial.
He has an alternative proposal, centred on unified management. Mr Kiley would keep the basic structure of the tube in one piece and use private-sector bidders as long term contractors under his control. One way of doing this would be for him to have a 51% holding in the companies.
However, the Treasury appears to have taken little interest in his ideas. One source said: "We cannot allow him to interfere in the day to day running".
Mr Kiley claims that the Treasury's plan amounts to little more than privatisation. What is needed, he suggests, is simple government funding of the necessary investment in infrastructure, which he estimates at £500m-£700m a year. "The 'fatal flaw' is simply that the public will own the system but not control it", Mr Kiley says of PPP.
What is the government's position?
It is complicated by there being distinct two camps - the Treasury, which wants to push through PPP, and the Prescott camp, which is more open minded about alternatives and has some of Mr Blair's sympathies.
Mr Kiley has painted a picture of Mr Brown, as "the Wizard of Oz", pulling the levers behind the scenes to control Mr Prescott, who is officially leading the talks.
The cost of reorganising the tube system could amount to £13bn over the next 15 years and the Treasury appears adamant that this should be kept out of public accounts, which an unmodified PPP plan does very neatly. They do not want taxpayers to be ultimately responsible for the risk, as they would be under Mr Kiley's vision.
The Treasury's argument is that, although the work would inevitably cost much more if done by profit-making, private firms, this would be recouped by the heightened efficiency of private managers.
Ministers are concerned that public-sector management is irreparably inefficient. They point to the Jubilee line extension, which doubled in cost to £3.5bn and was completed 18 months late.
The government are also concerned that, if PPP were not adopted, it would also leave Aslef in too powerful a position, as it showed today and earlier this month by closing almost all of the network for a day.
Related articles
29.03.2001: Tube strike causes severe disruption
26.03.2001: 'Safety abyss' fears for tube
26.03.2001: Further down the tube
20.03.2001: Bonds for beginners
19.03.2001: Safety fears stall tube deal
12.03.2001: Who's who in drive to improve the tube
Related special reports
Livingstone's London
Transport in London
Useful links
RMT
Transport for London
Treasury PPP plans
