‘Talk us through Operation Alexander.’

Natasha shrugged. ‘I told Miss Winkelman about it. Other units were dealing with subversion in all the European democracies and in America, but because of Dante and his position in MI6 – and the quality of intelligence and insight he was able to provide us with – 61a was by far the biggest and most important unit of its kind, and Alexander was its most significant operation, with maybe half the staff working on it. By the time I arrived, you had already been identified as the principal conduit.’

She tried not to let her humiliation show. ‘Why, if you don’t mind me asking?’

‘You were considered ambitious, single-minded, conscientious. And your unrequited love for Sergei Malinsky was viewed as an Achilles heel that we could exploit.’

The word ‘unrequited’ was like a blow to Kate’s solar plexus. ‘But I’m not sure I understand. Sergei was a GRU officer. Even if he’d been honest about our past friendship, how would the SVR have been aware of it?’ The GRU was Russia’s military intelligence arm and the rivalry between the two services was legendary. ‘Or are you saying they worked together?’

‘We hate each other, as you well know.’

‘So how could the SVR have been aware of our past friendship?’

‘I don’t know. You had been identified as the conduit before I joined the unit, so I wasn’t involved in those discussions. Maybe Dante recommended you. My job was to seduce Sergei and make sure he was aware that Igor Borodin was in the habit of hosting the cream of Russia’s intelligence hierarchy on his yacht in the late summer every year. We were confident Sergei – and you – would do the rest.’

Kate thought of one of the prime minister’s first questions to her in the South of France: who in the Service could have known of your friendship with Sergei?

The answer was very few. Yes, the friendship was technically listed in her personnel files, but not its depth and affection.

‘But nobody foresaw the possibility that you would fall in love with him?’ Julie asked Demidova.

‘Exactly. I was sent to Istanbul, where he was based and, well …’ She gave Kate a knowing look. ‘You understand.’

‘How come Sergei was posted to London?’ Julie asked. ‘The SVR can’t have arranged that.’

‘They already knew that was to be his next job. He had only a few months left in Istanbul by the time I arrived.’

‘You must have had to work fast,’ Kate said, and regretted it.

Natasha smiled at her. ‘I don’t think that becomes you, Mrs Henderson.’

Kate tried to smile back. ‘Who is Agent Dante?’

Natasha shook her head regretfully.

‘You said “his”.’

‘I think so.’

‘Why?’

‘I asked Igor about Dante once in one of our sessions. That was when he said “he”, but I have no more to go on than that. Maybe it was a generic expression. In Moscow, all agents are generally referred to as “he”.’