I checked his company online. Auracle Geospatial Science was a technology start-up that collected and analysed data from satellite, aircraft and drone platforms. There were examples of their work on the website: locating and surveying leaks, monitoring gas emissions, security, detection of oil spills and damage, the inspection of offshore oil platforms and flare stacks.

The Auracle office was in Astana’s Special Economic Zone, an industrial park in the heart of the capital: ten acres of tax-free start-ups occupying low, windowless units, the whole place surrounded by corrugated fencing and razor wire. According to the list of businesses at the front gate, Auracle shared it with a lot of warehousing and manufacturing plants for everything from pharmaceuticals to diesel engines.

I couldn’t get in without the kind of high jinks that were liable to see me arrested, but I suspected Auracle kept most of its business out of the office anyway: the production of satellites and lenses, the drones themselves. They’d need an office to arrange bribes for launch licences, somewhere to shoot the vodka, get the tax benefits.

From what I could tell, a lot of their work involved what, in the service, we called MASINT: Measurement and Signature Intelligence. I first saw the phrase in training, as we were familiarising ourselves with the various acronyms. MASINT was where it got weird. MASINT covered the data that human senses weren’t able to receive: ultraviolet and infrared radiation, alterations in the electromagnetic spectrum, variations in the gravitational pull of the Earth. These were monitored using hyperspectral sensors. All sorts of things revealed themselves.

Most of the interest for Six was in relation to collecting data on weaponry and bomb tests. It was only when I saw it being used by BP in Azerbaijan that I became fascinated by the imagery produced. I used to stay behind in the offices, scrolling across the data maps of Central Asia. Oil miles underground showed up as hydrocarbon particles in surface soil and water, but the more recent past was down there too. You could see the outlines of destroyed cities thousands of years old, make out mass graves, the Stalinist ones identifiable by their regular shape, then the fainter sites of what must have been Mongol and Scythian massacres.

Bryant’s geographical routine had been mapped by Joanna first, then Vectis as they searched for her. It didn’t deviate much; expats cling to routine and Astana offered few temptations. Office from 9 to 5, then an address on Saryarka Avenue which turned out to be a bar called The Rocks. After eight hours roaming the hyperspectrum, he hit the bottle hard.

I liked the sound of The Rocks. It was the sort of place I would have sought out eventually anyway. A city has currents like any sea. It was useful for a spy to know the places where loneliness swept a man. Whenever I arrived on a new posting I let myself be carried.