Gas suits and masks in the sun: London prepares itself for an Armageddon

From IRA bombs to Hitler's doodlebugs, the City of London is used to bracing itself in the face of terror. But never before has it taken 470 emergency workers in gas suits carrying Geiger counters on a sunny Sunday lunchtime to prepare for Armageddon.

At 11.48pm yesterday a crackly message from the driver of a Tube train stopped 50 yards inside a tunnel on the Waterloo & City line at Bank station signalled the start of the most high-profile counter-terrorism exercise in Britain since the 11 September attacks.

The rehearsal of the evacuation of a train trapped 100ft below ground by a poison gas attack transformed London's financial heart into a mass of police, firefighters and para medics practising decontamination and evacuation techniques against a backdrop of the Bank of England and the Stock Exchange.

Alastair Darling, the Secretary of State for Transport, said: "Most people realise we live in extremely difficult times. We've got to prepare against all eventualities."

Codenamed Osiris 2, the official aim was to test how the emergency services would deal with a chemical assault on the capital by deploying state-of-the-art stocks of protective clothing, antidotes and neutralising showers on to the streets in a quarter-mile square chunk of the City closed to traffic.

But beyond the practicalities of disaster control, the exercise - watched by 50 journalists and screened live by ranks of television cameras - was at least in part about a propaganda battle against al-Qa'ida.

Ken Livingstone, the mayor of London, appealed to the stoicism of Londoners, who have put up with the threat of Irish republican terrorism for decades. He said: "Throughout the long IRA campaign, we didn't allow it to make a great change to the way we lived in London. Nor should we do the same with this threat from al-Qa'ida. We had horrifying attacks in the 1980s but that didn't stop London being open for business. I think Londoners are quite rational about these things."

Whether they are also prepared for the sight of police in military-style respirators and charcoal-lined suits forming security cordons while dozens of choking commuters struggle for survival 100ft below remains to be seen.

A team of two British Transport Police officers arrived on the scene within seven minutes of the alarm being raised, climbing from their car carrying Geiger counters and air-sampling equipment.

They were then joined by an imposing force of about 40 police officers- part of a 200-strong police contingent - wearing gas masks and dark protective suits. They formed two security lines as they marched from the Bank of England. But it was not until 12.26pm, 28 minutes after the first fire engines had arrived, that crews of firefighters in new pale green gas-tight body suits - making each wearer look like a cross between a laboratory worker and a children's television character - began to enter the station "hot zone".

Organisers of Osiris 2 insisted that the test was not designed to assess response times or based on a specific substance. But sources indicated that the scenario was similar to the Sarin nerve gas attack on the Tokyo metro in 1995.

Less than 0.5mg of Sarin can kill in seconds meaning that many - if not all - of the 60 teenage police cadets who posed as stricken commuters down below would have been dead before help arrived.

London Fire Brigade initially said that its first teams had entered the station within 10 minutes of arriving through an unseen entrance. But the brigade later admitted that had not been the case.

Mike Bowron, assistant commissioner of the City of London Police, said that the delay was a necessary part of dealing with the suspected release of a poison gas, pointing out that among the casualties from the Tokyo attack had been emergency workers who first arrived at the scene and rushed straight beneath ground.

He said: "We don't want a situation where people rush in where angels fear to tread. A few minutes at the surface assessing what we have got to do could save an awful lot of lives. The purpose here is not assessing response times but deploying all this new kit and testing it in the field."

Below ground, 40 firefighters were sent down to reach platform seven of the Waterloo & City line and evacuated the 60 volunteers from the dimly lit train trapped in the tunnel.

As the first police cadets, aged from 14 to 18, were brought to the surface at 1.05pm, some warming to their role by coughing and spluttering on reaching fresh air, they were greeted by lines of ambulance and police in gas suits in a "warm zone" downwind from the attack scene. One of the youngsters, dressed in white overalls with kneepads, was overheard saying to a friend: "It's like being in a horror film."

After having their faces wiped with a sponge, each "victim" was provided with an instruction sheet telling them to cut off their clothes and don an orange cape, blue plastic gloves and black rubber shoes.

They were then put through one of two new mobile decontamination units - large space-age tents fitted with heated shower systems and neutralising chemicals which can handle 200 people an hour. During a week day, some 350,000 people work in the area.

The London Fire Brigade (LFB), which is facing a dispute with the Fire Brigades Union over a claim that its members should be paid more to use the chemical suits, said it expected to have the capacity to process 4,000 people an hour by the end of the year. Near by, a separate exercise was conducted at University College Hospital, where 20 decontaminated casualties were brought in and about 20 "walking wounded" turned up without warning.

Staff at the hospital, which had closed its doors for three hours and set up its own sterile zone guarded by police, said that they were treating all of the casualties as if they had been exposed to Sarin.

The Government, which said it was not responding to any specific threat by holding the exercise four days before the second anniversary of the 11 September attacks, said that Osiris 2, which is estimated to cost about £450,000, was designed to be as realistic as possible. Mr Darling said: "We must be prepared for any eventuality. People have to be vigilant and prepared. Today's exercise is about being as prepared as we can be."

It was not immediately clear what those taking part, including firefighters who for health and safety reasons had to lift dummies weighing 13 stone to the surface rather than the volunteers, had gained from the experience. When asked how his men would have coped in a real life with 600 rather than 60 commuters, Ken Knight, the LFB's chief fire officer, said: "Obviously, that's completely different."