‘I understand that. I have always found our prime minister’s personal morals repellent, though even I did not believe he would sink this low. But the fact that he is a profligate adulterer – even in this repellent way – does not de facto prove he is a Russian spy. And if we were to go ahead and accept this defection, we would be destroying him.’

‘We have a former head of the SVR – or at least his son – categorically stating that they recruited James Ryan to work for the Russian government while he was serving in Kosovo and that they used this video and enormous cash payments, the details of which they will bring with them, to blackmail and induce him.’

It occurred to Kate that she had never asked Mikhail if the video had been sufficient of itself to turn James Ryan, but the conversation was moving too fast now. ‘This is my point,’ Ian said. ‘What if the Russians are just using this to destroy the prime minister and cause maximum possible chaos and disruption to our political system?’

Normally a master of self-control, Sir Alan visibly struggled to maintain it. He stared at Ian with barely concealed disdain. Kate glanced at Suzy, who had the good sense to remain silent. She wasn’t looking at Ian with quite the same admiration now.

‘I’ll be honest,’ Simpson said. ‘What really troubles me here is the context. In the very first briefing note to me on this matter, you made very clear that you were not aware of any putsch within the SVR, the GRU, or at the apex of any other part of the Russian political system. This news has come out of nowhere.’

‘That is because we very rarely get a break at this level. We’re being offered an unprecedented opportunity that we cannot in all conscience turn down.’

‘But isn’t it just a bit too convenient?’ Ian asked, all innocence once again.

‘We lose nothing by proceeding. We have to give two people, who mean nothing to the public at large, asylum. Once they are here, we can all assess the video and the evidence of bank payments for ourselves. If we do not believe them to be genuine, we argue they came here under false pretences and act as we see fit.’

‘Except they will have a letter with my name on it. What would be our explanation for why I wrote it if we decided this offer was not genuine? I’d look naïve at best, downright stupid at worst. The prime minister would be livid that I had even entertained the idea and I wouldn’t blame him.’

Sir Alan shook his head curtly. ‘You have no choice, ma’am, I am afraid.’