The whole tale took twenty minutes, and by the time they’d finished, Knox was sitting in the single chair that faced Holland across his desk, Williams was perched on the thick arm of the sofa Miss Albury had had installed for the large meetings Holland refused to have in his office, and Bennett was standing next to the window that offered a view across Mayfair that was almost identical to the one from Knox’s office.

Knox could tell from the questions Holland poked each of them with that his curiosity had been piqued. He also realised why he’d been so nervous about this conversation. He’d craved a real mission, and now he had one: vindicating Williams and giving some kind of meaning to the hell he’d been through. But it was still up to Holland whether he’d be allowed to pursue it, or if it would just be swept even further under the carpet.

‘It’s too late to cancel the summit,’ Holland said finally. ‘Kosygin’s already in the city.’

‘I don’t want you to,’ Knox replied. ‘Dungeness proved there are some very dangerous people at large. If we did, or launched some nationwide manhunt, we’d just drive whoever it is to ground. But I’m willing to bet they’re in London right now, so we should use the opportunity we’ve been given to flush them out. And if they are Soviet illegals working against Kosygin, we can make a show of expelling them after he’s gone.’

Holland took his metal-rimmed glasses off and slowly polished the lenses as he considered what his deputy was proposing.

‘I’m still not convinced about the threat to Kosygin,’ he said. ‘But I agree that something strange is going on, and that the KGB’s illegals have been getting a little too confident recently. You won’t be able to get near Kosygin while he’s in the Russian embassy, though if something happens there it wouldn’t be our problem anyway.’

He slipped his glasses back on and looked at the clock hung between his door and a large painting of a crumbling castle on a headland surrounded by churning waves.

‘However, with Laing still recovering no one should be surprised if you stepped in to supervise our security arrangements,’ Holland continued. ‘Kosygin will arrive at the Trades Union Congress in an hour, then he’ll be at the Foreign Office with the prime minister, foreign secretary and president of the Board of Trade in the afternoon. I want you to go to both and watch who else turns up.’

Knox nodded, suppressing both a smile and his relief.

‘I’ll come too,’ Bennett said. ‘If Richard does spook anyone it’d be good to have another pair of eyes watching.

‘And vice versa,’ Knox added.

‘Agreed,’ Holland said.

‘What about me?’ Williams asked. ‘I might recognise someone.’