Driving his recently requisitioned mini-digger up from the roadway, Saul came to a concrete area enclosed on three sides by block walls, now overgrown with weeds and occupied by rusted-together piles of swarf and machine parts and an ancient truck probably belonging to a scrap dealer from some previous age. He recognized this area as a bay intended for mounding beet before they were transported away – from the time before such vegetables were wrenched from the ground by robotic harvesters, washed and then mashed up, before the mulch was injected straight into one of the many processing plants scattered across the local landscape.

‘You are heading in the right direction,’ Janus informed him. ‘Another twenty metres and you should be right over the entrance.’

It lay behind the beet bay, where brambles and nettles fought for predominance with GM beans, so there was no visible sign of it on the surface. Scraping downwards a metre through this tangle, he unearthed a layer of cracked concrete and managed to pull away a lot of this before revealing a rusted cast-iron lid. This he tore up to expose steps heading down underneath the beet bay. He picked up his torch, climbed out of the digger and descended.

Because it was concealed inside a hill, only the lower floor of the bunker had flooded. The large upper chamber and four side rooms were packed with all sorts of interesting rubbish: sacks of solidified fertilizer, a table and chairs made of plastic now as brittle as eggshell, a kitchen counter with an old gas stove, the gas bottle underneath it; a generator that had obviously broken down, then been taken apart and abandoned; some cups, plates and cutlery in decaying kitchen units which, judging by the date of a newspaper stuck to the table, must have been only a hundred years old. He had much work to do.

It took him a full month to get the required equipment in place. He first ran a buried power line from a harvester recharging station, then a pipe from the surrounding irrigation grid. Pumping out the lower floor revealed rotten crates filled with the rusted shells of food tins, and also an escape tunnel filled with rubble. After running a dehumidifier inside – one stolen from one of the grain-processing plants – he sprayed every surface with a layer of sealant. All the while he resided there, he kept the dehumidifier running and never required any of the irrigation water, instead using water leeched from air that was constantly moistened by the damp surrounding concrete.