So I picked up my torch and ducked back into the ancient ossuary, leaving the assault squad’s carbines where they’d fallen. They were too visible, their ammunition too hard to come by. But NATO 9mm – which the Grach’s magazine was loaded with – could be scavenged from any policeman’s belt. Why it wasn’t charged with the Russian armour-piercing rounds it was designed for could have been due to operational security or expediency – or because they weren’t serving military.

I crouched and listened but my hearing was shot. There was nothing to do but get out while I still could. I stretched out on my back and craned my head into the bone-pipe. I flicked on the flashlight, checked the integrity of the boot-damaged walls, and started the ascent – forcing myself up, clinging on to the crumbling foot- and handholds that I’d already half-destroyed in my first attempted surge to safety. I pushed and braced and squeezed and kicked, and emerged back into the world choking on bone dust, spitting out fragments of femur on to the damp cemetery ground at the base of an elaborate stone tomb. I rolled clear and lay flat, swallowing deep breaths of clean, crisp, night air.

The remaining grenade was the last thing that went down the chute after I came out – ensuring I’d be the last person to use it. Going off five metres underground, the blast hardly registered between the densely packed gravestones and mausolea around me. But I felt the vibration of bones and earth collapsing beneath me, and I knew that the entrance would be sealed.

I sat up and got my bearings. Low cloud. No moon. And no movement. The soft sodium light thrown by the street lamps that ringed the graveyard settled on the ancient stonework like an orange blanket. It made everything look unreal, insubstantial. But at least I could see. I needed to head south. How, exactly, I’d be able to keep moving, where, exactly, I’d go – I just didn’t know. But then, as I got to my feet, one of the alabaster angels presiding over the tomb I’d emerged next to lurched forward, arms thrust out at me. I jumped back and raised the Grach reflexively, not knowing whether I was under attack or whether the grenade had caused a cave-in. Then I saw. Smeared with tunnel slime, clothes torn, eyes bright in the darkness, the figure reaching out for me wasn’t an angel – but it was a saviour nonetheless.

I lowered the pistol and reached out, too, and clasped the muddy hand of Bhavneet Singh.

18

Zero eight thirty.