‘In the spirit of full disclosure,’ Callum went on, ‘what did she have to say about Agent Dante?’

Kate turned towards him, since his question was a lot easier to answer than Julie’s. ‘She claims she’s a protégée of Igor Borodin and had worked for a special unit he created called 61a to deal with the flow of intelligence from Agent Dante at the heart of SIS – and to run all the operations that stemmed from it. She suggested that everything we’ve seen in the UK – all of the operations Julie was just describing – have been the product of this unit, working hand in glove with Dante.’

‘And who is Dante?’

‘His identity is the greatest and most closely guarded secret in the Russian state.’

‘But definitely a “he”?’

‘She thinks so, but I thought her logic was pretty shaky on that point, so I wouldn’t stake my life on it.’

‘Perhaps it is Ian,’ Julie said. She was talking to Kate, but it was Callum who responded.

‘Why Ian?’

Kate sighed. ‘Because the only concrete piece of information she was able to give us was that Dante was recruited in New York in the mid-nineties and some of his early intelligence appeared to relate to UK position papers on Bosnia.’ She turned to Callum. ‘And Ian was our man in New York during that period.’

Callum whistled to himself.

‘But you see my point?’ Julie asked.

‘I do,’ Kate said finally.

‘Could you clarify?’ Callum asked.

‘Just when everything’s calming down,’ Kate said, ‘and matters seem settled, they stir it all up again with another golden nugget that seems to suggest, a touch too neatly, that Agent Dante just happens to be the new chief of SIS.’

‘And yet we’ve suspected Ian all along,’ Julie said. ‘Haven’t we?’

They fell silent after that and, back at the hotel, Kate was grateful to be able to retreat to the relative peace and quiet of her room. She sat on her bed for a long time, then went down to have a cup of coffee at a table in the corner of the terrace. She watched a gleaming white super-yacht moor where Igor Borodin’s The Empress had once been. It had three fake masts to make it resemble a tall ship.

Did she suspect Ian? Had she all along, as Julie had suggested?

Somehow she struggled to see Ian as a long-term traitor. But perhaps his neediness and insecurity were an act. He was clever enough, that was for sure. As he liked to remind people, he might well be the smartest person in the entire Service with a double first and cognitive scores that were off the chart. Too clever for his own good, Sir Alan had once said, and maybe there was some justice in that.

She sipped her coffee very slowly, trawling her memory for other signs over the years that she might have missed, but she kept returning to the question of how Agent Dante could have known that Sergei Malinsky was Kate’s ‘Achilles heel’.