Just after 7:30 p.m., Knox’s Jaguar turned into the underground car park beneath Leconfield House, and Knox, Bennett, and Williams went up to his office, where Knox requested every single one of Laing’s files on MI5’s preparations for Kosygin’s visit, and all Russia-related Pipistrelle chatter for the last three months, from the night clerk.

After two hours of combing through everything, Bennett unfolded herself from the armchair next to the teak cabinet that ran the length of one of the walls, announced that she needed to stretch her legs, promised that she wouldn’t leave the fifth floor or pick any locked doors, and left the two men alone.

‘You made it to the top,’ Williams said after he and Knox had spent another five minutes pretending to read the papers they were holding.

Knox looked at Williams, and then his office. They were sitting in the two chairs in front of Knox’s desk that stood between the long cabinet and wide window that looked out across Mayfair.

‘I did,’ he said.

‘You were always going to,’ Williams said. ‘That flat, the fifth floor. I’m proud of you. And I owe you an apology.’

‘You do?’

‘For my temper in the car, and under Smithfield.’

‘You remember them?’

‘I do. I even remember doing this.’ Williams dropped the folder he’d been holding onto Knox’s desk and held up his bruised, scabbed hands.

‘What’s changed?’

Williams shrugged his shoulders. ‘Something must have happened in the warehouse, or in Dungeness.’

‘You were near catatonic on the beach after the sniper started firing at us. Maybe that was some kind of trigger.’

Williams shrugged again. ‘Maybe.’

Knox put his own file down on his desk. ‘And you really think the KGB is behind all of this?’

Williams nodded. ‘I know I’m still not exactly a totally reliable witness, but it’s the only way I can think to make sense of everything.’

Williams told Knox more about the remnants of memory that seemed to be growing and knitting themselves together in his mind.

He could now clearly recall days spent in cold huts with views across Arctic tundra, then hours in hot, stuffy offices with no windows that felt deep underground, and being part of crowds walking through city streets past towering buildings and hard-edged statues. The details he could conjure up had convinced Bennett when he’d told her about them as he guided the MG from Haringey to Soho. And they convinced Knox as well. Knox had never been to Russia himself, but he was sure Williams was describing parts of the world on the other side of the Iron Curtain.

‘And now,’ Williams said, ‘whenever I close my eyes I see Kosygin’s face.’