Police have staged a mock attack on an underground train in London to prepare for what British security officials say is an almost inevitable terrorist attack.
Fire engines raced to Bank station underneath the Bank of England shortly before noon as firefighters struggled into green protective suits and descended to aid "victims" of the simulated chemical attack.
The drill, which lasted several hours, involved about 500 police, firefighters and paramedics rescuing about 60 "casualties" from a train trapped in a tunnel.
The theoretical chemical was described as "something like Sarin". Dressed in orange decontamination capes, the "victims" were then carried or herded up onto the street where they were washed down in yellow tents.
Britain's top police officer, Sir John Stevens, said last week that Britain faced a threat from suicide bombers and said his London force was on its "highest level of alert".
"We've got to test our response to what could happen in the event of a terrorist attack . . . whether its an attack at Heathrow or a chemical or gas attack on the London Underground," said Transport Secretary Alastair Darling.
Mr Darling confirmed there was a plan, called Operation Sassoon, to evacuate parts of London to "rest and reception areas" in the surrounding countryside in the event of a serious threat.
With the second anniversary of the September 11th attacks on the United States on Thursday, Washington's top ally London is considered a prime target.