Overcrowding which closed a busy Tube station in the rush hour today overshadowed a test run of Olympic-style travel conditions at five major rail stations.
The problem, due to a faulty train on the Underground's Northern line, meant passengers were prevented from entering King's Cross Tube station for 15 minutes just before 9am.
This prompted rail unions and politicians to question public transport's ability to cope with the Olympics which start in less than two-and-a-half weeks.
The incident happened as restrictions of the kind that will be used during the Olympics were given a "rehearsal" today at London Bridge, Cannon Street, Waterloo East, Charing Cross and Victoria main line stations in London.
Bob Crow, general secretary of transport union the RMT, said: "We have warned that the Olympics transport plan rests on little more than a wing and a prayer due to cuts to staffing and maintenance and this morning's closure of King's Cross due to a faulty train on the day of the official transport test has rammed that message home with a vengeance."
Labour's London Assembly transport spokeswoman Val Shawcross said: "With just 17 days until the Olympics start it is extremely worrying that major stations are being evacuated due to overcrowding.
"This kind of incident is bad enough, with the disruption it creates for people on the way to work, but during the Olympics this will lead to even more problems. It's time the (London) Mayor (Boris Johnson) and Transport for London got a grip on the Tube and prevent these kinds of problems from happening."
Passengers seemed less than enamoured with the Olympic rehearsals.
On Twitter, they spoke of "Olympic-geddon" and of customers ignoring signs and staff instructions.
But a spokesman for Network Rail said the tests had gone well.