There were just three of them in the room for the meeting, held upstairs in No. 10 amid the sombre paintings and the terracotta walls: Dr Gall, Lachlan Campbell, the national security adviser, and the PM. The latter was late – last-minute business following a typically bruising session of Prime Minister’s Questions in the Commons that afternoon. Dr Gall sat stiffly on the edge of her cushioned chair, while opposite her the national security adviser leaned back in his seat, arms behind his head, legs crossed, highly polished shoes and purple patterned ankle socks on display, in what Dr Gall thought was a completely inappropriate attitude for the gravity of the situation. At least he wasn’t manspreading. That was something at least.

‘Dr Gall,’ said the PM, brightly, as he entered the room, slightly out of breath, and sat down heavily on the chair next to her, ‘the floor is yours.’ But seconds later his genial smile of welcome faded as he heard what she had to say.

‘There’s no easy way to say this, Prime Minister,’ she began. ‘But what just happened in Svalbard could be every bit as serious as Salisbury. Or worse.’ Lachlan Campbell did not look so relaxed now. He uncrossed his legs and sat upright in his chair. ‘This could have grave implications for public health,’ she added. ‘We’re talking a potential pandemic here.’

For a long moment the PM simply stared at her, saying nothing as the colour seemed to drain from his face. ‘Go on,’ he said at last.

‘We’ve run the tests on the live samples taken from the infected patient, Sheila Mackenzie – who is still critically ill, by the way.’

‘And?’ prodded the PM.

‘And what she is infected with is an extremely dangerous pathogen. We call it “a chimera”.’

‘A what? Isn’t that a mythical beast?’

‘Well, yes,’ the Porton Down scientist replied, ‘but in our world a chimera is a genetically modified virus. In other words, someone has deliberately inserted the genes of one virus – Marburg – into another virus, one that resembles monkey pox, creating a kind of super-pathogen, if you will. We believe it could carry an extremely high mortality rate.’

‘Christ alive,’ breathed the PM. ‘Don’t tell me it spreads by inhalation like Covid?’

‘We think it does, yes,’ she replied.

‘Who would want to do such a thing?’ asked the PM.

‘This has to be a state actor,’ interjected the national security adviser, ‘and everything I’m hearing points to Moscow. I should have mentioned, Prime Minister, I took a call from Sir Adam from south of the river a short while ago. They’ve reached the same conclusion.’

‘Which is?’

‘That this is another bloody GRU operation. SIS believe the Russians were testing some kind of new biological weapon up there. Something went wrong and whatever it was they were testing leaked out … And ended up infecting our nationals at the research station.’