The more I scanned, the more evidence I saw that the fence was still being worked on. Lengths of metal and odd pieces of wire lay scattered on either side of it, and further up the hill, on the outside, was what looked like a small trailer which I assumed the builders had been using to bring up material. I’d been planning to cut our way through the bottom of the weldmesh, but with this amount of construction still in progress that seemed a dangerous idea. Instead, I decided to take a look at the stretch near the trailer, in the hope that it wasn’t yet complete.

For the time being we were out of the wind, in deep shadow, on dry ground, and as comfortable as could be – so I wasn’t surprised when Sasha began to snore gently beside me. I turned to look at him, and saw that his head was resting on one arm. Let him sleep, I thought. One pair of eyes is enough here.

Forty minutes later, I gripped him by the arm. He came to silently and was immediately alert. I pointed downhill, along the wire, where I’d seen the glow of a cigarette being drawn on. Then it came again, closer. A patrol was on its way round the perimeter.

I got the kite-sight aligned and saw the smoker immediately: a single man with a weapon slung on his shoulder. At his heel a German Shepherd was ambling, apparently loose.

‘Get ready!’ I whispered. ‘He’s got a bloody dog.’

I felt for my knife, down my right leg. I hate guard dogs. You never know whether to shoot them and give away your presence by making a noise, or risk serious injury by trying to get a knife into the bastards.

We lay on the bank like logs. I felt we were going to be all right, because the drift of the wind was from the fence to us, and we hadn’t put any scent on the ground by going to the wire itself. Besides, the sentry was an idle sod: he was ambling along, not looking to right and left, but humming to himself between drags. As he passed beneath us, within fifteen feet of our heads, the smell of cheap tobacco smoke filled the air around us. It wasn’t surprising that the dog never deviated from its track.

We gave the pair a couple of minutes to get clear, then went for the fence. Close inspection revealed that none of the wire was insulated, and that there was no alarm system that I could see. We moved cautiously uphill towards the trailer, and found it contained drums of more razor wire. Fifty metres beyond it we found what I’d been hoping for: a section of fence not yet fitted with the overhang. In twenty seconds we’d both climbed the weldmesh and gained the cover of the heaped tree-tops.