A police officer takes part in a mock chemical attack simulation at the Bank underground...

A police officer takes part in a mock chemical attack simulation at the Bank underground station in central London, September 7, 2003. The exercise, which does not involve members of the public or real chemicals and is designed to test London's ability to cope with a terror attack, began at 1048 GMT on Sunday and is designed to test the response of the police, ambulance and fire services to such an incident. The scenario being acted out is that a chemical is released on a busy train travelling from Waterloo to Bank station in the heart of the City of London.