Tarpin said, ‘What I do with your wife is my business,’ and he laughed at his own joke. ‘And you can fuck off out of it.’

Beard was stalled for a moment, for it was not a bad line, and in this hiatus it occurred to him that what he wanted, no, intended to do, any second now, was to kick Tarpin’s bare shin very hard, hard enough to break a bone. The prospect thrilled him and made his heart beat faster. He could not remember if it was these boots or some others thrown out long ago that had the steel tips. It did not matter. How odd, that the man he had once irrationally half-despised as an intruder into his domestic peace, with his drills, tuneless whistling and unbounded dust-creation, and puerile station jabbering on a tinny radio all afternoon, this hireling was now his adversary in equal combat. Only Beard would have considered it equal. Over many years, his colleagues had noted, and sometimes despaired, that in confrontations – theoretical physics naturally had its share – Beard possessed the gift, or curse, of recklessness.

‘You hit my wife,’ he said, his voice constricted by his racing pulse.

He had already glanced down and seen the angled plane of Tarpin’s shin, white, flecked with sparse black hairs like an ill-plucked turkey. And now Beard, something of a sportsman in his day, despite his height, was shifting his weight onto his left foot. He would remember to spread his arms for balance, and if there was time enough he might half turn and crush a toe beneath his heel.

It did not occur to him how obvious it was that he was about to attack. His rounded chest heaved plainly, his thin arms were raised and tensed, and his face was strained, lost in the solipsism of an exciting plan. It was likely that Tarpin had been in many scraps as an adult. Before Beard could duck, Tarpin had drawn back his arm and lashed the older man’s right cheek and ear with an open-handed smack. Beard’s consciousness exploded behind his eyes, and for seconds afterwards the world was a humming white blank. When it seeped back, Tarpin was still there, clutching at his towel, which had loosened with the movement.

‘The next one’ll hurt,’ he said.

This was the kind of treatment old-fashioned movie heroes used on the woman they loved, to calm them. The builder regarded Beard as unworthy of a proper punch. But clearly, more was on the way. Fortunately, at that moment there came from next door the sound of children’s voices approaching up the path, and whispered exclamations and suppressed giggles at the sight of their near-naked tubby neighbour. Then three shy faces at different heights and three pairs of wide brown eyes peered over the fence. Tarpin hurried into the house. He might have gone to fetch a larger towel, or a coat, and it seemed to Beard a good moment to be on his way. But he had his pride and was careful not to appear in a hurry. As he walked down the drive, past the boat slewed in its cradle and the recumbent phone box, he felt his face stinging and burning in the cold – that slap really hurt – and there was a continuous sound in his ear, an electronic whine, and by the time he reached his car he was giddy and half deaf. As he started the engine he looked across at the house and, sure enough, Tarpin in tracksuit and trainers with flailing laces was coming towards him with a firm stride. Beard saw no good reason to linger in Cricklewood.

In the remaining three weeks of that year, everything began to change. There arrived an invitation to the North Pole – at least, that was how he described it to himself and everyone else. In fact, the destination was well below the eightieth parallel, and he would be staying on a ‘well-appointed, toastily-heated vessel of richly-carpeted oak-panelled corridors with tasselled wall lamps’, so a brochure promised, on a ship that would be placidly frozen into a semi-remote fjord, a long snowmobile ride north of Longyearbyen on the island of Spitsbergen. The three hardships would be the size of his cabin, limited email opportunities, and a wine list confined to a North African vin de pays. The party would comprise twenty artists and scientists concerned with climate change, and conveniently, just ten miles away, was a dramatically retreating glacier whose sheer blue cliffs regularly calved mansion-sized blocks of ice onto the shore of the fjord. An Italian chef of ‘international renown’ would be in attendance, and predatory polar bears would be shot if necessary by a guide with a high-calibre rifle. There were no lecturing duties – Beard’s presence would be sufficient – and the foundation would bear all his expenses, while the guilty discharge of carbon dioxide from twenty return flights and snowmobile rides and sixty hot meals a day served in polar conditions would be offset by planting three thousand trees in Venezuela as soon as a site could be identified and local officials bribed.

Word soon got round the Centre that he was going to the North Pole to ‘see global warming for himself’, and some said he would be towed by dogs and others that he would be pulling his own sledge. Even Beard was embarrassed, and let it be known that it was ‘unlikely’ that he would get all the way to the Pole, and a good part of his time would be ‘in camp’. Jock Braby was amazed by Beard’s commitment to the cause and offered to arrange a send-off party in the common room.

In the same week as the North Pole summons he began an affair with a not-so-young accountant he had met on a train and asked out to dinner. She was pleasantly dull, worked for a fertiliser corporation, and it was all over in three weeks. Crucially, however, the edge of his obsession with his wife was blunted – minimally, and not all the time, but he knew he had crossed a line. It saddened him, to know that he would soon stop desiring her altogether, for it gave him a view of the obvious truth, that it was already over and that the comfortable house and their possessions would have to be divvied up, and after a year or two he might never see her again. Visiting Tarpin had also helped initiate his disaffection. How could he continue to love a woman who wanted a man like that? Why punish herself so thoroughly just to insult her husband?

What else did he not know about her? One answer came just before Christmas, in a long-delayed conversation that became an understated row of cold finality. She had known for half a year that his mathematician from Humboldt, Suzanne Reuben, was barely a tenth of the story. Patrice had most of the rest of the truth and, pacing and despoiling the sitting-room floorboards in her stilettos, enumerated tersely the names, places and approximate dates, a dossier memorised with an obsessiveness that matched his own. The cheerfulness she had shown around the house, she said, was to conceal her wretchedness, the affair with Tarpin was supposed to save her from humiliation. She demanded to know how Beard was going to explain away eleven affairs in five years. He was about to remind her of his mother, who ran up a higher score, when Patrice left the room. She had come to talk, not to listen. Here it was at last, the confrontation he had been wanting all these months. Now he could not think why. He lay on the sofa, legs propped on the glass coffee table, closed his eyes and felt the first longings for the cold pure air of the treeless Arctic.

In late February he arranged to leave from the Centre for Heathrow, and so the farewell party in the communal room took place while his taxi stood outside, and his bag stuffed with his old skiing clothes waited by the door. Sixty-one people were now employed full-time, and most of them crowded in to hear Jock Braby’s speech, for this was more than a send-off, it was a celebration of the shining steel object mounted on two crates in the middle of the room, a prototype designed and constructed in record time, ready to be tested in the Farnborough wind tunnels, Tom Aldous’s quadruple-helix wind turbine. Many noted how it resembled in more intricate form Crick and Watson’s model without the base pairs, and some tried to remember and adapt Rosalind Franklin’s famous remark that it was too beautiful not to be true, or, in this case, not to work. In his speech, Braby reminded the team that it was too early for congratulations, there was far more work to be done, but he wanted everyone to see just how far the project had progressed, and how revolutionary it would be. With uncustomary lyricism, he summoned an image of a townscape, as seen from a nearby hill, and five thousand roofs glittering in the setting sun with the gyrations of their silver turbines, far more beautiful, he thought, than the TV aerials that had transformed the urban prospect in the nineteen fifties.