After a quick diversion north, I peered over a pipe at the transit van which had caused my panic. It was parked a good two hundred yards away, in front of one of the other active buildings at Pyestock, but its presence was unnerving.

"I want to stay well out of sight of that."

Which is why we made a circular route into the network of pipes to the east of the Air House before crawling under, or clambing over various obstacles to get to the next building. The gravel didn’t help, making our movements obvious to anyone with ears. But we quickly found our way to the next building and set about trying to find a way in.