IF ANYONE HAD been driving along a tiny Wiltshire lane called Manor Farm Road an hour before sunset on that Tuesday afternoon, they would have been shocked at the speed at which a blue-and-yellow police car was travelling. It was no ordinary patrol car. With a top speed of close to 170mph, the Lotus Evora was the fastest vehicle in use by any police force in Britain. It needed to be. Inside a locked and sealed medical container resting on the back seat were three samples, all taken from a live patient at the Royal Free Hospital in north London: Dr Sheila Mackenzie. One was blood, one was urine and one was ‘exudate’ – fluid seeping from the open lesions that had begun to appear on her forearms. All three samples had been inserted into sealed flasks, then passed through a ‘dunk tank’ containing six per cent bleach to reduce any risk of contamination and infection.

No member of the public witnessed the Lotus Evora screeching up to the entrance gates of the Defence Science and Technology Laboratory at Porton Down that afternoon. That was because police patrolmen on motorbikes had already closed off the last mile of the route, turning away all traffic. Porton Down had been chosen by Whitehall because it was the only laboratory in the country capable of identifying the microscopic pathogens teeming and multiplying inside those flasks. And every second counted for this analysis.

The guards outside the gate had been radioed ahead. They lowered their stubby black high-powered Heckler & Koch MP7 carbines and raised the barrier as soon as the Lotus swept up the chestnut-lined drive. ‘Response level heightened’ read the updated security status on a board displayed beside a chain-link fence that ran the length of the avenue leading up to the entrance. The police Lotus drove on, only slowing down at the last moment for each of the speedbumps. Escorted by two of the on-site patrol cars, it swept into the high-security scientific compound. Past the admin blocks, the neatly mown lawns and the road to the open-air testing range, until they pulled up at the large building containing the BSL4 – the Bio-safety Level 4 laboratory – with its array of silver chimneys belching out their thin plumes of white vapour, all extracted, sanitized and expelled from the labs.

There are four ‘suites’ within that building and Level 4 is for only the most dangerous organisms on the planet, fatal pathogens such as Ebola or Crimean haemorrhagic fever. The tests that were needed now were about to be conducted in the bio-containment laboratory reserved exclusively for Level 4 agents. Since the work was classed as a national security priority, the job was given to two of the most experienced scientists on the books.