‘That case is closed, I’m afraid.’

‘But I would need to know the background, would I not?’

‘I don’t believe so, no.’

‘But if my life is also to be at risk—’

‘It won’t be.’

‘Given what happened, I don’t see—’

‘The file is sealed. That’s all I can say.’

‘But these allegations that the prime minister is a Russian spy—’

‘Unproven, which is why the file is sealed.’

Suzy didn’t flinch, or back down. ‘If I’m to take this role, Mrs Henderson, I’d appreciate knowing the background. That’s all.’

Kate was tempted to wonder aloud why she was under so much pressure from her superior, Ian, to take this woman as her new deputy. Good for interdepartmental relations, he’d said airily, though he’d been fiercely territorial at even the hint of an incursion from MI5 across the river until his ambition to be the next chief had got the better of him. He’d been turning himself into the ultimate Whitehall warrior.

She leant back in her chair and stared out of the window at the morning commuters hurrying through the rain outside Vauxhall station – the unchanging backdrop to her working life. She’d ideally love to send this woman back across the river where she belonged, but she recognized that, given the questions over her own recent past, she’d probably lost the ability to determine this aspect of her future – and many others. ‘It was called Operation Sigma,’ she said. ‘We received intelligence that a group of senior Russian intelligence officers used to meet regularly on a super-yacht owned by Igor Borodin, a former head of the Russian Foreign Intelligence Service, the SVR.’

‘Of course I know who he is.’

‘We – I – recruited a young au pair to take a job as nanny to Igor’s grandson onboard. We persuaded her to plant a bug in his study. Shortly afterwards, we recorded him and his colleagues discussing the fact that the former prime minister had cancer and was about to resign. It was clear that one of the candidates to replace him was working for Moscow.’

‘Which one?’

‘Well, you’ll have seen the leaks in the press—’

‘The current prime minister, yes, but was it correct?’

‘In the end, there was no way of proving it either way, which is why the case was sealed.’

‘Did you agree with that decision?’

Kate hesitated. ‘We cannot afford to see a democratically elected leader’s mandate undermined without hard evidence.’

‘Do you think he was guilty?’

‘My view is immaterial. We need to be an evidence-based organization, particularly in this world of disinformation and lies.’

‘What happened to Rav?’

‘He was murdered.’

‘But the coroner’s verdict was suicide?’

‘Look—’

‘And as I understand it, he – indeed all of the work of Operation Sigma – was betrayed by an agent in your midst, planted here to assist the current prime minister’s rise to office.’

Kate gazed at her icily. Bloody Ian, she thought. This woman was far too well-informed. So much for the file being sealed. ‘That matter is also closed.’