In my mind I brought back into as sharp a focus as I could manage a set of intelligence maps we’d been shown of Moscow in 2009. We’d been given them for good reason: to help familiarize ourselves with the location and construction of a brick and glass monstrosity that was an almost straight rip-off of the MI6 building at Vauxhall Cross on the Thames. Not two kilometres from where we sat waiting at a red light was the one building in Moscow I wanted most to avoid. Rising up on the south side of the airfield – and home to all manner of spies and sharks – was the now fully operational headquarters of the GRU. There was no doubt about it. We were heading straight for the Akvarium.

I was sitting on the right side of the vehicle. I curled my fingers around the door-release but to no avail. I looked at the safety screen more closely. Half-inch bullet-resistant plexiglass recessed into the chassis. I looked at the passenger windows, too: also reinforced. I was trapped. I guessed I’d enter the Akvarium the same way I was always taken into Vauxhall Cross: via an underground tunnel that emerged in a secure area. I would have no opportunity to run – because there would be nowhere to run to.

In a couple of minutes I would be swallowed, lost. The Akvarium was rumoured to be so labyrinthine, and internal access so heavily restricted, that whole sections of it remained mysterious even to the people who lived and worked there. It was an entirely self-contained and self-sustaining state within a state: water, electricity, food, living quarters, weapons, manpower – and even, General King had said, one of Russia’s three cheget nuclear briefcases, a key command and control component of the Kremlin’s Strategic Nuclear Forces. Once I was inside the Akvarium, it would be the GRU calling the shots, and no one else.

I ran my hands through the daysack. I needed a miracle. I felt for anything I could use as a weapon or to force a lock. My right hand closed around a small can of aerosol deodorant in the washbag, my left around the barrel of a plastic lighter. I thrust them both into my jacket pockets.

The traffic cutting across us from south-east-bound Leningradsky Avenue stopped. The lights turned green. But before we could move, the front passenger door opened and a heavily built man with a buzz cut climbed in and sat next to the driver. He turned and smiled through the reinforced glass. I looked around. The Range Rover had pulled in behind us. They must have been waiting to see where I was heading. Now they’d decided to spring the trap.

We inched forward. I looked at the driver and then past him, out the left-hand window, scanning the road for signs of more operators. The car lurched. And then my ears filled with the slip-shunt bang-crack of metal colliding, crunching, smashing.