“I know, but some of us can’t be spared.” Nunn transferred the weight of his forearms on to the steering wheel, managing to convey his disinclination to talk. The sky ahead had cleared to an antiseptic pale blue, but the ground was still wet, and the car’s wheels made swishing sounds on the tarmac curves as it descended towards the airfield and flying boat terminal at Chivenor. Nunn continued to drive fast, with broody concentration, as the view of the estuary was lost behind a row of dripping evergreens.

Hasson, slouched uncomfortably in the rear seat, stared at the 8 back of his chief’s neck and wished there had been no reference to the clearing of the flight corridors. His plane was due to take off in little more than an hour and the last thing he wanted was to think about the possibility of it smashing into any human bodies which might be drifting through the low cloud and fog that often obscured the Atlantic air lines.

Nobody in the west had any clear idea of what was going on in the vast tracts of land spanning the eastern hemisphere from the Zemlayas to Siberia, but each winter a sparse, slow blizzard of frozen bodies — kept aloft by their CG harnesses — came swirling down over the pole, endangering air cargo traffic between Britain and North America.

The general belief was that they were Asian peasants, ignorant of the dangers of boosting to even a modest altitude in a continental winter, or victims of sudden weather changes who had been claimed by frostbite without realising what was happening to them. A hysterical faction, small but vociferous, claimed they were political expendables deliberately cast loose on the geostrophic winds to hinder, even marginally, the flow of western commerce. Hasson had always regarded the latter idea as being unworthy of his consideration, and the fact that it had entered his mind now was yet another pointer to his state of health. He slid his hand into his coat pocket and gripped the container of Serenix capsules, reassuring himself they were available.