"Postponed," Toby muttered in Greg's ear. "That's all."

"Right, get them down there," Mark was saying.

Kendric and Hermione began to descend the ladder to the diving platform. The crewmen were holding the fully rigged hovercraft steady in Mirriam's wake.

"You'll have to take our cuffs off," Greg pointed out.

"Maybe we'll just throw you down," said Toby.

"Take 'em off," Mark said. "And you two, don't think about jumping."

Greg just managed the climb down the ladder, frightened his weak, trembling hands were going to lose their grip. He flopped down in the bottom of a hovercraft, exhausted and horribly woozy.

Gabriel sat on a bench next to him, breathing heavily. One of the crewmen cuffed them both again.

"Are you all right?" Gabriel asked, her face anxious.

"Yeah."

He heard the fan start up, an incessant droning whine. There was a surge of motion, then the deck tilted up as they climbed the levee wall. The dizziness returned.

When they were down the other side, he struggled into a sitting position against the tough plastic of the gunwale, trying to take an interest in the journey. The sour-faced woman was perched on the rear bench, her waterproof zippered up against the occasional scythe of spray. Her hair was blowing about in the slipstream.

One of the Mirriam's crewmen was up front, steering from behind a little Perspex windshield. A bodyguard was sitting behind him, giving Greg and Gabriel the occasional impersonal glance. At least Toby wasn't on board. He managed to get his eyes above the gunwale.

It'd taken centuries to drain the original fenland marches and turn them into farmland; generations had laboured to liberate the rich black loam from the water, rewarded with the most fertile soil in Europe. The polar melt drowned them in eighteen months. The Fens basin wasn't a sea, it was mud, tens of metres thick with a tackiness gradient that varied from a few centimetres of weed-clogged salt water on the surface down to near-solid treacle.

An ex-Fenman living in Oakham had once told Greg that it was possible to tell the age of a Fens house by looking at its doorstep. The older it was the more the loam would've dried out and contracted beneath it, leaving the doorstep high and dry. Really ancient cottages had a gap below the bottom of the stone and the ground.

Greg couldn't see any doorsteps; on the few lonely farmhouses still visible he was hard pushed even to see the doors.

Twelve years of sluggish tidal suction had chewed out their foundations, pulling them down into the absorptive alluvial quagmire. Some of the sturdier buildings had managed to retain their shape, upper floors rising out of the brown-glass surface over which the hovercraft were racing. But the majority had subsided into tiny flattened islands, with juncus rushes growing out of the shattered bricks and skeletal timbers. Ragged felt hems of blue-green algae encircled all of them.

The hovercraft took a gently meandering course, avoiding the solid protrusions and swollen semi-submerged branches of dead copses in wide curves. Greg and Gabriel were following Kendric's craft, slicing through the fine spray its passage whipped up. Behind them, the horizon was marked by a fine green line. The Nene levee. Which meant they were heading approximately south. It didn't make any sense to Greg. There was nothing ahead of them.

Nobody lived in the basin. Crabs and gastropods thrived in the nutrient-rich sludge. But no one could earn a living from catching them. An ordinary fishing boat would stick fast in the mud. Conceivably a very light sail-powered catamaran or trimaran might be able to move about. And the idea of deploying nets or pots was laughable. In fact, hovercraft were just about the only vehicles which could be used successfully on the Fens basin.

From being the most fertile tract of land in Europe the Fens had reverted into a zone of barren desolation rivalling the Sicilian desert for inhospitableness. The sheer sameness of the quagmire was numbing Greg, bleeding away any last reserves of hope and defiance into the stifling atmosphere. Endless kilometres flowed past, compounding the sense of isolation. Gabriel had hunched up in her seat, defeated.

His attention drifted. Analysing his predicament was suddenly futile, tiresome in the heat and moisture. His thoughts began to freefall, wondering what Eleanor was doing right now. And please don't let Kendric think she was important.

"Greg."

The urgency in Gabriel's voice made him look round quickly. A town was rising out of the horizon's uncompromising interface between brown and blue. It was like a mirage, its base lost in the black and silver ripples of shimmering inflamed air. Kendric's hovercraft was powering straight for it, leading them in.

"Hey."

The bodyguard sitting behind the pilot turned, boredom reigning. "What?"

"Where are we?" Greg asked.

"Wisbech. Why, does it make a difference?"

He should've known. Wisbech was the harbinger. The self-declared Capital of the Fens was the first instance of wholesale evacuation in England. At the start of the Warming, excessive rains and record tides had sent the Nene cascading over its banks. And in those days the river ran straight through the centre of the town.

Greg had remained glued to the flatscreen for a week while pontoons of news channel cameras chugged through the flooded streets. He remembered the pictures of drowned orchards ringing the town, the sodden refugees slumped apathetically in Royal Marine assault boats, clutching pathetically small bundles of possessions. It was something out of the Third World, not England. The novelty of such scenes had paled rapidly in the months, and then years, which followed, as town after town succumbed to the water.

Wisbech only looked whole from a distance, close-up it was in a sorry state. The outskirts had collapsed completely, leaving a broad inverted moat of rubble, protecting the town's heart from the larger vagaries of the swelling mud tides.

Both hovercraft slowed, manoeuvring cautiously around hummocks coated in vigorous growths of reeds. The narrow channels between them were choked with algae, so thick in some places it resembled a green clay. It was stirred up by the hovercraft's downdraught, freeing pockets of rancid gas. Gabriel and the crewmen coughed and swore, clamping their hands over their faces, Greg couldn't smell a thing; his throat began to dry, though.

Five metal streetlamps marked one channel for them, miraculously remaining upright after all these years, The conical algal encrustations around them were actually solidifying, turning them into cartoon desert islands. From the height of the poles left above the surface Greg guessed that the street must've been about one and a half metres below the hovercraft.

Further in, the mounds became more regular, the channels echoing the street pattern they covered. Sections of walls had survived here, triangular, cracked, and leaning at crooked angles. The brickwork was obscured by a viscid pebble-dash of gull droppings. An eerie desynchronised harmonic from the electric fans was bouncing back off them, amplifying their natural soft purr to a vociferous clattering reverberation.

Overhead, hundreds of gulls twisted in devious helices, calling shrilly, the high-decibel feedback from the entire flock a brazen fortissimo rolling across the ruins. Greg realised it was impossible to creep up on Wisbech.

They swept out of the mounds and into a suburb that was still standing; two-storey houses bordering a light industrial estate. The mud came halfway up the ground-floor windows.

There was no glass left in them. Second-storey windows were shattered, crystalline shark teeth sticking out of mouldering frames. Walls bulged, roofs sagged alarmingly, shedding tiles like autumn leaves. Gutters were wadded with grass and bindweed.