The prime minister excused himself with a glint of triumph in his eyes and Andrew gave Kate and Julie the details of how they ran Incisor. He lived in a flat by Gorky Park, between Leninsky Prospekt and Donskaya. Each morning, he left the house at 6 a.m. to walk through the park and across the bridge to an open-air swimming pool called Chaika, or Seagull. On Thursdays – when he swam as part of a morning club – they managed the exchange of information through a leather bag left in a locker three along from his own in the changing room. If SIS wished to communicate with him on any but the appointed day, a yellow car would be parked outside the swimming pool, alerting him to the need to check the locker in question.

After his swim, he would return home, pick up his dog and take it for a walk around Gorky Park. If SIS had requested an emergency meeting, it would ‘clean’ his progress all the way to the pool and back, then through the park to a café called Ostrovok, where he was in the habit of drinking his morning coffee and reading a paper. If he wished to trigger an emergency meeting, he would take a different cut-through from Leninsky Prospekt. Andrew punched up a photograph on the screen they shared. ‘It leads past a restaurant called Kafe de Marko here.’ He switched photographs. ‘If everything is proceeding as normal, he takes his usual route here.’

‘Is there not a danger in meeting so close to home?’ Julie asked.

‘We don’t think so. We devised this system with him. He was adamant he wanted something that could be meshed into his daily routine. We’re a long way from SVR Headquarters here, and few of his colleagues live in this area – which is why he moved here. He’s something of a loner and has assured us he doesn’t know any of his neighbours. There’s no immediate prospect of bumping into anyone he knows in this part of the city.’

It was an agent handler’s recurring nightmare: the possibility of a random coincidence in which either the source or, worse, the handler bumps into someone either knows in the middle of a sensitive operation.

‘We haven’t attempted a meeting with him since we set him up,’ Andrew said. ‘And since then, we’re down to two facilitators. So we’re going to need your help. I suggest you and Julie take the park. We’re more familiar with the topography around the pool and the journey to and from it. The park is more straightforward. And it leads into the meeting itself. You think you can handle that?’

‘Of course,’ Kate said. ‘Will he be expecting to see one of you?’

‘No. We’ve made very clear to him that he’s dealing with a system not an individual or a series of them. You will say, in Russian naturally, that you’re waiting for a man called Boris, and would that be him by any chance? He’ll smile and say, no, he’s sorry, he can’t help you there – but you’re welcome to join him while you wait. You’ll take a seat and say that Boris is very late.’ Andrew leant forward towards the camera. ‘I want a promise from you, Kate.’