By politics.co.uk staff
The tube strike has hit Londoners hard, with millions of journeys rocked by the industrial action.
Maintenance workers, drivers, signallers and station staff walked out in two phases last night in a dispute over redundancies.
Many analysts are treating the strike as an opening skirmish in the battle between the government and the public sector.
Speaking on the picket line by King's Cross Station, RMT union leader Bob Crow apologised to commuters for the inconvenience but warned more strike actions could come if the mayor and London Underground continued with their plans.
"We have laid out the clearest possible evidence to the mayor and his officials that if he breaks his promises and slashes station staffing numbers he will be giving the green light to disaster," he said before the strike.
Boris Johnson said the redundancy plans were "moderate and sensible".
Eight hundred jobs are set to go on the underground. Unions argue that the lack of staff in stations will make them more insecure, but management insists there will always be at least one member of staff in each station.
Transport for London (TfL) insisted a third of its trains were running today but union leaders' claims that support for the strike rock solid seemed more convincing.
Only the Northern line was working normally. All other lines were severely disrupted.
Mike Brown, of London Underground (LU), said: "We are doing everything possible to keep as many Tube services operating today, and to keep Londoners moving.
"Londoners will face some disruption, but the city is not paralysed and people will still be able to get around."
One hundred extra buses and an increase on passenger spaces on Thames riverboat services were laid on, and some taxi ranks were marshalled. Escorted bike rides and walks also tried to assist Londoners get to work.