‘I don’t believe it.’ Suzy Spencer was Kate’s former deputy, who’d been attached to the Service on secondment from MI5 after the death of Rav, her close friend and ally. Suzy was, on any reasonable analysis, an absolute snake.

‘Yes, you do. She let Ian shag her at exactly the right time.’

A key turning in the lock signalled Shirley Grove’s arrival, followed by a huge man carrying a Nespresso machine and a Waitrose bag full of every variety of milk. He unloaded it into the fridge before offering Julie his hand. ‘Hi, Callum Ellis.’

They were momentarily lost for words. He was more than six feet tall, with shaggy dark hair, a rangy beard and a chiselled jawline that framed his face, which was about halfway between those of Daniel Craig and the late George Michael. He wore chinos and a tight T-shirt, beneath which his ripped biceps seemed to be struggling to escape.

Kate caught the slightest hint of a smile playing around Grove’s lips. ‘You want coffee?’ he asked. He had a broad Mancunian accent, with a guttural, rough rasp.

They wanted it very badly.

‘Jesus Christ,’ Julie hissed, as he turned away. ‘You could have warned me.’

‘I’d never met him,’ Kate whispered. ‘He’s Grove’s sidekick.’

‘Bloody hell. She’s a dark horse.’

Callum slipped into barista mode and they moved to the conference table Grove had installed in the back room.

‘All right,’ Grove said. ‘Callum is going to need to start from scratch.’

‘From the very beginning?’

‘Yes.’

‘My name is Kate Henderson and, until very recently, I was head of SIS’s Russia Desk. Julie worked with me. We had a source I’d known from my days as a student in St Petersburg who had been posted to the Russian Embassy in London. His previous assignment had been in Istanbul and he told me he’d learnt while there that the cream of the Russian intelligence hierarchy routinely gathered on a super-yacht owned by Igor Borodin, the former head of their foreign intelligence service, in the summer months. We recruited a young nanny to work with Igor’s son. She managed to plant a bug on the yacht.’

Callum was looking at her intently. He didn’t seem to blink.

‘That was where we overheard the suggestion that the former prime minister had prostate cancer and was about to resign. It was clear from the drift of the conversation that one of the leading candidates to replace him was a Russian agent of influence. Our subsequent investigations led us to believe very strongly that this was James Ryan. And, in the course of that process, we also discovered that my husband Stuart was working for Moscow and quietly assisting him. He is now in exile.’

Kate took a sip of her coffee. ‘A few months later, we got a message from Igor Borodin that there had been some kind of coup in the securocrat class in Moscow that had left him vulnerable. He said he wanted to defect and would bring with him firm evidence of the prime minister’s treachery in the form of the sex video used to blackmail him.’