Adding to the stress factor, the labour union RMT announced industrial action by staff in some parts of the city's transport network during the Games to demand bonuses in recognition of the extra work involved.

Weary Londoners accustomed to almost daily problems on the Tube, the world's oldest urban underground railway network, have been predicting for years that the overstretched system would struggle to cope with the Olympics.

The Monday morning rush hour seemed to confirm their worst fears as they were met with announcements over the speaker system that the Central Line was suspended on its busiest stretch while the Jubilee Line was running at a snail's pace.

Compounding the misery, a key overground link was also "experiencing severe delays".

These announcements were met with disbelieving rolls of the eyeballs as the Central Line, Jubilee Line and Overground all go to Stratford, site of the Olympic Park and focus of years of infrastructure improvement efforts.

"This is going to be brilliant for the Olympics," said one passenger on the crowded but at least functioning Northern Line, to guffaws from fellow commuters pressed into the carriage like sardines.

The Central Line closure was due to a passenger on the tracks, hardly the fault of those running the Tube. But ominously, the Jubilee Line delays were caused by faulty platform-edge doors at North Greenwich station -- gateway to several Olympic venues.

The Overground's problems were due to a signalling failure, one of London transport's most common ailments, according to the announcements.

"It's been a bit of a nightmare. They seem to be understaffed. I'm not sure they're going to be able to cope," said Mike Troughton, 30, emerging from busy Liverpool Street station.

The RMT said staff from South West trains would refuse to work overtime throughout the Games, while staff at Serco, the company that runs the bicycles-for-hire known as "Boris Bikes" after the capital's colourful Mayor Boris Johnson, would take similar action during the first weekend of the Games.

Some staff at Transport for London, including those manning information telephone lines, would strike for short periods during the opening weekend, the RMT said. These actions are all over demands for Olympic bonuses.

"Although we have secured good deals on Olympics recognition and reward for the vast majority of our members we still have a small number of employers holding out," said RMT boss Bob Crow in a statement.

"We cannot accept that blatant unfairness and the time has come for these employers to seize the opportunity, get round the table and sign off agreements that recognise the additional work and pressures that these staff will be carrying." (Reporting and writing by Estelle Shirbon; Editing by Peter Rutherford)

• A Permanent Economic Emergency