‘Paperwork and computer files relating to the development of Killer-T were seized, along with samples of a vaccine. Preliminary tests at the Porton Down biocontainment facility indicate that the vaccine is at least ninety-five per cent effective and has no immediately obvious side-effects. A few moments ago, the DNA patterns and other details for manufacturing this vaccine were deployed to hundreds of vaccine laboratories around the world.

‘I would like to personally thank the police officers, military personnel and scientists who have taken part in this operation. And to offer special thanks to the member of the public, who wishes to remain anonymous, but whose vigilance may save millions of lives.’

Shouts came from the gaggle of media the instant the prime minister stopped talking.

‘Prime Minister, if the raid took place early on Thursday, why are you only announcing it now?’

‘Couldn’t the anti-virus samples have been released sooner?’

‘How long will it take to manufacture enough of the vaccine for everyone?’

The prime minister cleared his throat. ‘My scientific advisors are in a better position than me to answer detailed questions and will be available shortly. Given the sophisticated nature of the plot, we felt it was essential to conduct preliminary safety tests on the vaccine before releasing it for manufacture.

‘Over the past two years, my government has put unprecedented resources into preparedness for another outbreak of a synthetic virus, and twenty-fold advances have been made in the speed with which vaccines can be manufactured, tested and deployed. The first batches of vaccine will be released to healthcare professionals and other essential workers within twenty-four hours.

‘As with all vaccines, there will be a period of between twelve and twenty-four hours before a patient has a high level of protection from Killer-T. Given the rapid spread of the disease, and the time it will take for widespread vaccine distribution, we can still expect the number of cases and fatalities to increase sharply over the coming days. I must urge everyone in the United Kingdom to continue to follow quarantine rules and await announcements on the vaccination programme in their area.’

As the prime minister stepped back into number 10, Charlie turned and smiled at her foster parents.

‘Looks like we got lucky this time,’ Navid said.

Charlie nodded.

‘But even with …’ She paused as the phone in her pocket vibrated. ‘Cases of Killer-T are at least doubling every twenty-four hours. So if it takes a week to vaccinate most people and another day or two for their bodies to develop immunity … That’s two to the ninth power … Making five hundred and twelve infections for every one we have now.’

‘But quarantines should significantly slow the infection rate,’ Navid pointed out.

‘True,’ Charlie said, pulling out her phone, which now had Mango’s name on the screen. ‘Sorry, I’d better take this.’

Charlie’s regular phone wasn’t encrypted so Mango spoke cautiously.

‘Have you seen the news?

‘Just watched it,’ Charlie said.