‘We have, frankly, hundreds of leads that all have to be discounted,’ continued Pullover. ‘The current population of Barentsburg settlement is four hundred and ninety-one inhabitants, of whom just twenty-seven are Ukrainians and nearly all the rest are Russians. That gives us nearly five hundred potential selectors with mobile numbers, all routing their comms through Russian-monitored masts, and all names that we need to run through our own systems.’

Luke noticed that one of the Norwegians was getting twitchy, looking like he wanted to interrupt. But the senior operations officer wasn’t done yet.

‘So how do we narrow this down?’ he asked the group. ‘We start by looking at their travel patterns. We can see who’s recently arrived and—’

‘Excuse, please.’ One of the Norwegians had his hand up. ‘We should please mention the Marjata? Our communications ship offshore?’

‘Absolutely,’ replied Pullover, cocking his head deferentially to one side. ‘I was just coming to that. So, yes, working with your NIS people in Oslo, we’ve gone back over the intercepts picked up from Svalbard over the past seven days and there’s certainly one that sticks out like a sore thumb.’

‘Excuse me?’ The Norwegian again. ‘A sore what?’

‘I’m sorry, it’s just an expression. I was referring to the burst transmission two days ago.’ The Norwegians were nodding knowingly now. ‘It was what we call a VOIP, a voice over internet protocol. We traced it to a known GRU number. It’s registered to number three Grizodubovoy Street in Moscow. That’s the headquarters of Russian military intelligence. They’re already on our cyber-threat database as part of what we call APT28. That stands for “advanced persistent threat”. And, yes, we immediately alerted our sister agencies.’ Now he was looking meaningfully at Luke and Jenny. ‘First thing yesterday, just in time for the weekly NSC meeting.’ He paused, then grinned, as if imparting a shared joke, before adding, ‘Sometimes the heuristics pay off!’

The heuristics? Brilliant, Luke thought. I have a 2:1 degree in international relations from Edinburgh, plus a decade and a half of government service, and I have no effing idea what this guy is on about. ‘Sorry,’ he interjected. ‘Heuristics? You’ve got me there.’

‘Oh …’ Pullover seemed disappointed that anyone needed the term explaining. ‘It just means intuitive shortcuts. We’re not all geeks here in Cheltenham, you know! Sometimes we simply have to work on a rule of thumb.’

Luke turned to Jenny again. ‘You didn’t know that term either, did you?’

Jenny gave him a withering look. ‘Luke, I’m a scientist. Of course I know what heuristics means. Now come on, pay attention.’