Kallie was twenty-four years old, but held no memory of those fabulous sun-soaked times before the great freeze. Like a man blind from birth, he had not even been granted the pleasure of memories. Bennett was a year or so older, and swore he could recall laying in long grass with the sun in his eyes, so light and bright it hurt to look into the sky. But almost everything that came out of his mouth was a lie. He said he had seen shops open in Oxford Street. He said he knew people who could take them South, far beyond the reach of the ice. He said if they waited inside long enough the government would find a way to make it warmer. All lies. But he was right about one thing; they could not survive without food. That was why Kallie let him go. They had been living on beans and tinned luncheon meat, which was edible if you made a couple of holes in the lid of the can and gently heated it over the stove. But ten days ago the last gas ring had ceased to work, even though the council had promised to keep the pipes clear. There was no news coming in at all now that Mr Jakobowski had stopped calling by. Perhaps it was over; the last warm body had chilled to a blue cadaver and the city was finally a postcard snowscape.

And perhaps Bennett had found a pub open somewhere and was spending his money with a bunch of his drunken mates. Kallie knew there was nothing for it but to find out for himself and go outside. He would certainly die if he stayed here. His last source of heat – the gas ring – had packed in. The electricity still worked intermittently, but there were no electric radiators to be had, not unless you were rich enough to buy one on the black market. There was nothing left to eat except boxes of dry cereal, and he hadn't any milk to put on them. In the last few days, the temperature in the apartment had plunged, although he imagined it was still a long way above the subzeros in the street below. It hadn't helped that he had thrown his typewriter through the window in a fit of temper two days ago. The keys had jammed, and he lacked the patience – and the required agility of his numbed fingers – to repair it. What alarmed him more was the fact that he no longer really cared what happened to him. It would be easy to escape this bitter place; he just had to open all the windows, remove his greatcoat and lay down on the bed for a few minutes. Perhaps that was his only choice. But not just yet. Not before he visited the outside world one last time.

He added an itchy red woollen sweater to the other layers of his clothing, then wound a scarf around his chest. Over this he struggled into his greatcoat, dug out leather gloves with split seams, tucked his jeans into the tops of his battered Caterpillar boots.

When he unlatched the front door and looked out, he was surprised to find snow drifting in the hall. It had been nearly two months since his last foray into the streets of what had once recognisably been Camden Town. The tall windows at the end of the floor had been broken by children, and the snow had formed a drift below the sill. If any of his neighbours still lived in the building, they were not prepared to answer his knock. Kallie rapped on Mr Jakobowski's door and listened with his ear placed to the peeling brown paintwork.

'Mr Jakobowski, I'm going outside. Do you want me to get you anything?'

He was sure he could hear someone moving around in the sitting room, but what could he do if the old man wasn't prepared to let anyone help him? In these strange times, who knew how people would behave? Something electrical hummed beyond the door. It sounded as if he had a radiator running in there. People jealously hoarded their heat sources. Who could blame them? Heat was hard to share; if you opened the circle it dissipated. He called a few more times, then gave up. In the past, when he had found anything he thought the old man might like, he would haul it home and leave it against his door. But the good-neighbour rules were no longer in force; now it was every man for himself.

Down the icy stairwell – the lift had not worked in thirteen years – to the front door, which was so frozen shut that Kallie assumed no-one had been in or out since Bennett had left with the contents of his wallet. Deadening whiteness glared in through the window panels. He would need to find sunglasses. He had tried to pick up ski equipment from Lillywhites the last time he was in town, but – surprise, surprise – they had sold out. Only a handful of staff still manned the store, keeping up the old conventions. He had worked there himself once, bored out of his mind, waiting to seize upon the odd straggling customer who had made it in through the snow. That was back when the market was still trying to cope with the crisis, when the rich warm nations were still exporting to their poor frozen neighbours. Now that those neighbours had ceased to earn wages, there was no point in supplying them with affordable products. The milk of human kindness had been the first thing to freeze.

Throwing his weight against the door, he shifted it wide enough to push his way through. Bayonets of ice divorced themselves from the lintel and fell about him, cutting stencils into the swathes of snow that crusted the steps. Kallie raised his face into the biting wind and looked along the street, in the direction of the city. The air stole his breath, forcing a gasp with the realisation that it was far colder than anything he had experienced before.

Snow dunes, sparkling like hills of granulated jewels, swept in great unspoilt arcs across a bleached Sahara of roads and pavements. This was a bad sign; the route had been passable the last time he ventured out. But now even those high-profile charity missions the government was fond of announcing had ceased while everyone sorted out the problems in their own back yards.

On his last trip, Kallie had seen a few heavy-traction vehicles lumbering toward town. No people, though. There were never any people. It was simply too dangerous to set out on your own. He vaguely recalled a shopping expedition with his parents, and some friends of theirs who owned a car fitted with snowtyres. His mother had bought crazy things, pointless things, floral dresses and summer blouses she would never be warm enough to wear. Anxious to be rid of their stock, the storekeepers had been bargained down to nothing. He would always remember his mother laughing in front of the mirror as she held the diaphanous chiffon material against her. Ironically, her refusal to lose hope had brought her to a protracted, painful end.

What had instilled his parents with such unreasoning optimism? Was it because they remembered a time when their world was a cacophony of movement and sound, when trees still flowered, when their vision was saturated with rainbow colours? Had they never lost sight of life's possibilities? Is that why they had allowed him to be born?

It took forty minutes to reach the deserted high street, silent but for the wind that moaned eerily around the corners of buildings like a widow at a wake. At Camden Lock the ice in the canals had expanded and crushed itself upwards into fantastic twisted geometries. Kallie pulled the fur hood of his coat tighter around his face and concentrated on placing one foot before the other. The secret was to keep moving, always keep moving.

There were no shops open at all in the high street. This was a worrying new development. Surely some signs of life still existed? In the last few years he had seen fewer and fewer people on the crystalline streets. Many had found ways of moving to the southern hemisphere. Some had chosen to stay because they were determined to rebuild their lives in the face of the changed climate. And there were the others, the ones who had no money and no way of leaving alive.

As he trudged on, staying wide of the treacherously deep drifts, he remembered a picture he had seen once, a framed tube poster from the 1930s. The fanciful painting showed a gigantic cherub with translucent blue skin, a symbolic representation of the North Wind, perched on the roof of Oxford Circus tube station, breathing icy air down over the scurrying populace. The message was something about getting in out of the cold. Such bright pigments, such warmth, all gone now, gone forever. The sheer white force of snow and ice blotted every other colour from the landscape.