IN MUCH the same way as you might put up a child’s painting with jolly fridge magnets, the scientists at Porton Down put little magnetic labels on the doors of their research laboratories: Bacillus anthracis, Yersinia pestis — anthrax and bubonic plague to you and me — and so on. These labels let the people in white coats know what is beyond those doors before they walk in. The labs are negatively pressurised so that any leaks are sucked in, not out. Every day, in they go, the research scientists whose work aims to ensure that you and I survive one of our worst nightmares: the release of a biological weapon by terrorists. This is the front line, the hermetically sealed battleground where preparations are being made for a war we cannot afford to lose.

Terrorism and defence experts, including Eliza Manningham-Buller, the head of MI5, say it is a matter of when, not if, we have to face the challenge of a biological, chemical or radiological attack. The question is: are we ready for it? To find out, I am allowed a rare visit to the Health Protection Agency’s Centre for Emergency Preparedness and Response at Porton Down, Wiltshire, where, for almost 100 years, scientists have conducted research into biological and chemical agents — today, strictly for defensive purposes. Not only do experts work on the actual bacteria and organisms that terrorists might choose, they also act as the hub and control centre for planning the response to any chemical, biological or radiological attack.

One reason for that is the proximity, next door, of the Defence, Science and Technology Laboratory (DSTL), the Ministry of Defence-operated facility that carries out research into chemical weapons such as sarin, the nerve agent released on the Tokyo underground system in 1995. That attack, by the Aum Shinrikyo cult, killed 12 people and affected 5,000 more.

At the HPA’s section of the complex, scientists spend most of their time protecting citizens against naturally occurring diseases. Some, such as West Nile virus, could be brought into the country by innocent carriers from abroad. But the scientists also produce vaccines and antidotes to combat the more sinister organisms that they fear terrorists might already have identified as their weapons of choice.

After 9/11 widespread panic was caused across the US when anthrax spores scientifically tailored as weapons were mailed to US government offices, killing five people and infecting 22 others over two months. Ricin, a toxin produced from castor beans — and which a small group of terrorists was caught trying to manufacture in London — was also mailed to the White House and the US Senate in 2003. The risks, therefore, are real. So what is being done to protect you and your children?

The scientists at the Centre for Emergency Preparedness and Response have been co-ordinating planning for attacks involving anthrax, plague, tularemia, smallpox and other bacteria since the HPA was set up in April 2003. It is funded by the Department of Health, but reports only to the Secretary of State for Health. At the lab that the photographer David Bebber and I are allowed to visit, the magnetic signs tell us that anthrax, bubonic plague and tularemia have all been recent visitors.After passing through a pressurised chamber the lab appears surprisingly low-tech, save for the microbiological safety tanks where cultures are handled through toughened rubber sleeves. The seriously high-tech equipment is in another part of the building, where new vaccines are being developed. We are not allowed to say where this laboratory is.

The man in charge here is a microbiologist, Allen Roberts, who goes by the exotic title of Group Leader, Novel and Dangerous Pathogens. In the event of a biological weapon release, his team has the task of quickly — very quickly — identifying the disease. He and his colleagues have all been vaccinated against the worst risks, including anthrax.

“We have a 24-hour capability, with four teams of four working a seven-day rota, one week on, one week off,” he says. “In the case of an emergency we have people permanently in contact with pagers. If we are sent samples from a potential outbreak, it is no good growing cultures or having tests that take 48 hours because people need to be treated immediately.

“We have developed tests using the DNA of the pathogen (the organism that causes a disease) so we can tell health specialists what we are dealing with, sometimes within six hours.”

Working in the lab today are Debbie Nash and Steve Welch. The latter, a molecular biologist who helped to develop the fast diagnostic tests, says: “We spend most of our time analysing samples from outbreaks of diseases that occur naturally, but we are ready for a deliberate release. There is a sense here that our work could be vital in saving lives.

“When I talk about my work to friends I find that they are a little more alarmed than they should be. Yes, our work is potentially dangerous, but there are tried and tested regimens in place and safety is paramount. The diseases we work on are treatable. There are other scientists here working on diseases that are potentially fatal.”

Indeed there are. We are in what is known as a Containment Level 3 lab. In the level 4 facilities, whose locations are a closely guarded secret, haemorrhagic diseases such as ebola — commonly known as a flesh-eating disorder — are being studied. Any accidental exposure to those could result in death. On a lower floor is the emergency response control centre headed by Dr Nigel Lightfoot, the direc tor of Emergency Response Capability, and Gordon MacDonald, the head of Emergency Strategic Planning. There are no flashing lights or military-style command displays; just people hitting the phones, watching their computers and monitoring 24-hour news channels. Across the country, in nine regional centres, there are 2,700 HPA staff, 460 of them here.

Lightfoot and MacDonald describe themselves as “co-ordinators, not doers”. Quietly, over the past few years, they have been pulling together skills that already existed among medical staff and the emergency services so that a response to any chemical, biological and radiological attack should run like clockwork. “We have had simulated exercises involving up to 200 people from the emergency services, hospitals and local authorities where there has been an imaginary release of sarin, a smallpox outbreak, a dirty bomb, a release of chlorine gas, and so on, all over the country,” says Lightfoot. “In each case, we get the emergency and health services together and throw a problem at them to see how they would respond. From each exercise we’ve learnt new lessons and implemented them. We are improving all the time, but if you were to ask are we ready, I would say yes.