‘So, against my better instincts, I took a seat, drank whisky and smoked, which I haven’t done in years. And the story came tripping out. She said she wanted me to get a message to Downing Street that the operation to smear the prime minister had been dreamt up by Igor Borodin, the former head of the SVR in Moscow, working in conjunction with an Agent Dante at the heart of SIS. I said I found it all a bit hard to believe. Why was she telling me? I asked. Because, she said, she couldn’t go through any of the normal channels. Agent Dante was so senior at SIS that any attempt to route the information through MI6 would lead to him being alerted.’

‘Him?’ Kate asked.

‘That was what she said.’

‘Are you sure?’

‘Yes, but it might just have been a figure of speech.’

‘Do you think she knew who Dante was?’

‘She said she couldn’t tell me.’

‘Which means she didn’t know.’

‘Possibly.’

Kate nodded at her. ‘Go on.’

‘I asked her how she knew all this. She said because it had been her job to feed this information to one of her colleagues – a man called Sergei – who had a contact of his own high up in SIS who would likely fall for the entire operation.’

‘Why?’ Kate felt her cheeks reddening.

‘She said the SIS officer was very ambitious. And in love with the conduit she was using.’

Kate wondered if Tess knew or had guessed that she was the officer in question.

‘She said she and this Sergei had become lovers. And then he had died in mysterious circumstances while travelling from St Petersburg to Moscow. She said she was devastated and left fearing for her own life.’

‘What did she want in return for this information?’

‘Nothing.’

Kate tapped the table in front of her. ‘Did you and Natasha become lovers that night?’

Now it was Tess Winkelman’s turn to blush. ‘I’m not sure that has anything to do with it. But, yes, as a matter of fact, we did.’

‘Have you seen her since?’

‘No. I mean, yes. We see each other at the tennis club every morning, but she’s avoided running into me – or even meeting my eye.’

‘Thank you, Miss Winkelman. You’ve been very helpful.’

An hour and a half later Kate, Julie and Callum had gathered in a corner of the terrace watching the bright lights shimmering off the waters of the Bosphorus. It was still warm and Julie was lathering herself with mosquito repellent. ‘Gratuitous question on the sex,’ she told Kate. ‘But who’d have guessed it of old Tess? What a goat.’

‘Goat?’ Callum asked.

‘You can talk,’ Julie said. ‘Your jaw almost hit the floor. You were panting at the very idea of it.’

Kate leant forward. ‘Callum, in the nicest possible way, I need to speak to Julie for a minute, so would you mind?’

He uncrossed his legs and wiped the smile from his face. ‘We’re all in this together, Mrs Henderson. I have complete security clearance, as you know. And if we’re going to come out of this in one piece, I reckon we need to decide now whether or not to trust each other.’