A mock terrorist attack has been staged at a central London Underground station, to see how emergency services would cope with the real thing.
Scores of 'casualties' were treated in the Square Mile
Dozens of police cadets pretended to be casualties of a chemical attack, with firefighters and ambulance crews getting the chance to test millions of pounds worth of new equipment.
Nick Raynsford, minister for Civil Resilience, said the exercise appeared to have been a success, although "there will of course be lessons to learn for all those involved".
The government has said the rehearsal did not take place in response to a specific threat and was part of ongoing anti-terror measures.
The exercise began shortly before midday, when the train driver reported the attack and stopped it in a tunnel 50 yards short of Bank station.
About 500 firefighters, paramedics and transport workers then worked to recover and treat the 60 'casualties' on board, bringing them to street level to decontaminate them in special shower tents.
The area immediately surrounding Bank station was cordoned off and designated as a "hot zone", while decontamination units were set up in a surrounding "warm zone" upwind of the centre of the site.
Staff at University College Hospital, which closed its doors for three hours during the operation, were also involved.
'Victims' arrived at the hospital about 90 minutes after the mock incident and were treated by medical staff in protective clothing.
BBC security correspondent Frank Gardner said the aim of testing the new equipment and coordination between the emergency services was a success.
But he said the controlled conditions of the rehearsal - which was carefully planned months in advance - could only achieve so much.
"If this were real life they would probably have had thousands of terrified members of the public to deal with and that would be a very different story," Gardner said.
Chief fire officer Ken Knight said a real exercise involving the closure of the busy heart of the city would not have been practical.
Assistant chief ambulance officer Philip Selwood said the biggest difference between Sunday's exercise and a real chemical attack would be that the effects of some substances may not be immediately apparent.
"Scores of casualties could begin presenting themselves at hospitals around London at different times following an attack," he said.
Mayor of London Ken Livingstone said the exercise would help save lives in the event of a terror attack.
He said: "We recognise if someone's prepared to give their life in order to kill, it's most probably impossible to stop them getting through.
"Our job is to put into place the things that minimise the loss of life when they do get through."
And Transport Secretary Alistair Darling said: "We want to test the new equipment that's available to the emergency services, we want to make sure London's resilience is as strong as possible," he said.
But Tory homeland security spokesman Patrick Mercer argued that Britain still lags far behind the US in terms of readiness for a terror attack.
"Sadly, there is no comparison - each American policeman is fully trained in nuclear, biological and chemical warfare," he said.