Knox had spent the night going back over every event of the last week, every piece of evidence, and every supposition. He was still convinced there was a Russian mole, but it wasn’t Manning. He’d made a list of everyone in MI5 who might have both reason to betray the Service and the access to information valuable enough to be worth something to the Russians. He went through the list again and again, and every time he came to the same conclusion. The mole had to be Peterson.

It wasn’t just the most logical possibility. It was also, embarrassingly, the most simple one. Peterson had been the one who had overseen Knox’s suspension, then orchestrated bringing him back in, both apparently under Manning’s orders. He was the only person in MI5 apart from White who knew that Knox had found Bianchi and Moretti’s secret papers. And, as Manning’s right-hand man, he’d see any information shared by the CIA, which would have led him to Valera.

He’d played the part of the harried deputy perfectly, all the while using Knox’s hatred of Manning to blind him to what was really going on.

‘I went snooping, as you suggested,’ White said. ‘And discovered that Peterson had quietly activated a safe house in Kennington. He’d tried to hide the order, but not very well. There was no way I could come and talk to you last night after the stunt you pulled at RIBA, so I went to see your American friend. She’s been keeping watch overnight.’

‘What happened?’ Knox asked.

‘Five minutes ago she called me from a phone box in Berkeley Square to tell me that a man fitting Peterson’s description arrived at the safe house this morning and left again with Miss Valera. They’re now at the Richmond Hotel on Conduit Street.’

So Knox was right. Peterson had kidnapped Valera under orders from the KGB, and he was going to use the conference as cover for getting her out of the country.

‘He killed Bianchi and Moretti, and now he’s going to hand her over to the Russians,’ Knox replied. ‘I need to stop him.’

‘Yes, you do,’ White replied.

‘And you’ve come to break me out of jail?’

‘Almost,’ White said. ‘Punch me.’

‘Excuse me?’

‘You can’t send anyone else to help Bennett, and I can hardly despatch my engineers as cavalry. It has to be you. But you also can’t just walk out of here.’ He squared up to Knox. ‘So punch me, make your daring escape, and I’ll make sure you get a head start.’

‘Are you sure?’ he asked. There had been plenty of times Knox had wanted to give him a right hook, but this wasn’t one of them.

‘I wouldn’t have said it if I wasn’t. You’re wasting time.’