In the long silence that followed, she held his gaze. ‘Who do you work for, Sergei?’

‘You know the answer.’

‘But that’s the thing. I’m not sure I do.’

‘I work for the Russian government.’

‘The GRU?’

He didn’t reply, but in this case she took his silence to indicate consent.

‘Why did you tip me off that Igor, Vasily and the others would be on that yacht in Istanbul?’

‘Does it matter?’

‘Yes.’

‘To help you.’

‘Why?’

‘Because in all this time I have not been able to get you out of my head.’

‘My colleagues think you told me what was to happen on that yacht in an attempt to discredit your rivals in the SVR.’

‘And you? What do you think?’

‘I . . . don’t know.’ And as she said it, she was aware that she really didn’t. Not honestly. ‘I don’t believe you would cynically mislead me.’

‘What else do we have to rely on in life but our instincts?’

Now Kate was wishing she’d gone a lot slower on the vodka. ‘All the same, that leaves the possibility that you told me the truth, which also happened to be in your interests and those of your organization. There would be nothing dishonourable in that.’ He was looking out of the window, at the snow falling across a ghostly landscape. ‘I need to ask you something else,’ she said. ‘Is it true that Vasily Durov has been deposed as head of the SVR and is under house arrest?’

‘He’s not under house arrest. Not yet.’

‘But the Kremlin has turned against him?’

‘There is a battle. It is not clear who will come out on top.’

Kate searched those big dark eyes. She was not sure how much longer she could keep up the pretence of professional detachment. ‘We have been offered evidence of our prime minister’s treachery.’

‘What kind of “evidence”?’

‘The details of how and when payments were made and a copy of the sex video used to entrap him, filmed with underage girls while he was an army officer serving in Kosovo.’

Sergei nodded, as if entirely unsurprised. ‘Who has offered it? Durov?’

‘Igor and his son. They also feel under threat as a result of their alliance with Durov and are convinced the net is closing in on them here. They are prepared to give it to us in return for asylum in the West. So is the video real or fake?’

‘I don’t know. But you need to be careful, Kate.’

‘Of what?’

‘You think, after all these years, that your husband was the Russian state’s only asset at the heart of British in telligence?’

‘Who else?’