It was a mercy the bar was so large. The two men were singing loudly in unison a comic song in Spanish and there was much laughter each time the chorus came round. For all his time in this corner of the United States, Beard did not understand a word. He raised his hand for another drink and it was with him almost immediately and he was digging it out from under the rubble of ice. Was ever a marriage dissolved so painlessly? Within a week she had left for the hill farm in Powys. In the course of a year they exchanged a couple of postcards. Then one came from an ashram in India, where she remained for three years and from where she sent one day her cheery acceptance of a divorce, all papers duly signed. He did not see her until his twenty-sixth birthday, at which she appeared with a shaved head and a jewel in her nose. Many years later he spoke at her funeral. Perhaps it was the ease of their parting in the old rectory that made him so incautious about marrying again, and again.

With some difficulty, he got to his feet and made his way across the rotunda bar towards the lavatory. By local standards, which were high, he was not an exceptionally fat man. Even now he could see a couple who easily outranked him, a man and a woman obliged by their shape to perch on the edge of their armchairs. But Beard was a fat man just the same, and his knees hurt and he felt dizzy from having stood too quickly. As he crossed the lobby, one of the clerks came out from behind the reception desk and hurried after him.

'Excuse me, Mr Beard, sir? I thought it was you. Welcome to the Camino Real? There was a gentleman looking for you?'

'Mr Hammer?'

'No. It was about a week ago? From England? But he didn't leave a message?'

'What did he look like?'

'I guess, kind of large? And said his name was something like Turnip?'

They would have continued with their questions, but at that moment Beard saw Hammer coming through the glass entrance doors, preceded by the porter with a luggage trolley. As the two men embraced, the clerk moved away with a self-effacing grimace and Beard nodded thanks in his direction.

'Toby!'

'Chief!'

Ever since Hammer learned that this was what Beard was once called, he had taken it up, in an ironic way. Others on the project had adopted it too and Beard, of course, was pleased. It almost made up for having been sacked from the Centre.

He was three years older than Beard, and was lean and strong and had the straight back, the clarity of eyes and skin of a man who had not touched a drink in twenty years. Although he walked bandy-legged, like a saddle-weary cowboy, he still played squash and backpacked alone in the High Sierras. Or he said he did. After time in his company, Beard often put himself on a diet that lasted many hours. Hammer's background was in electronics, but in the early eighties he decided to become a drunk and wreck his marriage and drive all his friends away in the customary manner. Once he was through his recovery and had got everyone back, including his wife and children, he began to develop work that had no clear job description. He knew people and introduced them, and fixed up deals. He introduced Beard to the tax-break lawyers and accountants who knew the state legislature, the go-betweens in Washington who patrolled the vast and vague territory between commerce and politics, and people who had a line to the grant-givers of the big foundations, the venture-capital types who knew people who knew friends of men like Vinod Khosla and Shai Agassi. Hammer steered Beard's patent applications through, secured the lease on the land near Lordsburg with a right to buy, learned to find his way around the solar fraternity and knew the engineers and the materials specialists. He had even squeezed money out of the Bush people in their dying days and, recently, far more from the bounty of Obama.

But Hammer could not protect the project from delay, and progressive shrinkage and, at times, near-complete collapse. There was compromise at every stage. The site in Lordsburg was a fourth choice in the American South-West. There were more sunshine hours per year in parts of Arizona and Nevada, but competition from the big utilities had pushed up prices. Other locations had no water, or no good road or nearby connection to the grid, nor such a friendly local Chamber of Commerce. The company he and Beard and others formed had been forced to reconstitute three times over to qualify for tax breaks. Homeland Security were suspicious of Beard's alien status, and letters from prominent American science academies made little difference in the Bush years. Money was hard, even in the good times. Among the venture capitalists who cared about solar, the consensus was that the two best bets were on the tried and tested routes, solar thermal – focusing the sun's heat to make steam to drive turbines – or photovoltaics – generating current directly from sunlight – and in both cases, concentrating the light with magnifying lenses. Reliable and cheap artificial photosynthesis was twenty years away, was the general view.

To disprove it, in early 2007 Beard mounted a demonstration to potential backers in a parking lot outside a lab in Oakland, California. The idea was that in full sunshine a large bottle of water would be split into its constituent gases, which would cause a fuel-cell generator to power an electric jack-hammer with which a man in a green hardhat would destroy a wall which bore the graffito 'oil'. But certain vital parts failed to be delivered, the meeting was postponed for a month, and then only half of the investors showed up and the project got one third of the money and shrank a good deal more.

The technical difficulties grew as the money declined. Tom Aldous had been correct in his general assumptions, and wrong in certain particulars, though Beard could hardly complain now that he owned seventeen patents. For a long time the little lab model that split water in 2005 could not be scaled up or made to work faster. The light-sensitive dyes that drove the process had to be reconsidered. The catalyst was not derived from manganese, but from a compound of cobalt, and another from ruthenium. Choosing and testing the right porous membrane to divide hydrogen from oxygen should have been easy but was not. The time came at last to design and build the prototype that one day would be mass-produced. An outfit near Paris was chosen. The panel, the glorious achievement, was two metres square and cost three million dollars. It was sent away for testing at the National Renewable Energy Laboratory in Golden, Colorado, and was found to be underperforming by three hundred per cent, and flawed in both design and construction.

They started again with a Chinese company sixty miles from Beijing. The tubes containing the light-harvesting semiconductor, the aqueous electrolytes and the membrane were of plexiglas on top, with a base of conducting stainless steel. The panel that housed the tubes was three metres by two, and each unit cost four million dollars. Once in mass-production, they would cost ten thousand dollars, so the business plan said. According to the lab at Golden, the new panel worked. By then, the world was in recession. Many promises made to Hammer were broken. The option on the land, renewed three times already, was expiring. Toby renegotiated and instead of the four hundred acres, bought twenty-five, right by the water source. There were now two small gas-storage tanks instead of eight giants, only one compressor for the hydrogen, one generator instead of five, and, worst of all, because they were the core and symbol of the project, a mere twenty-three panels tilted skywards instead of one hundred and twenty-five.

But they were finally in place, and the day after tomorrow a new chapter would begin in the history of industrial civilisation, and the earth's future would be assured. The sun would shine on an empty patch of land in the boot heel of south-west New Mexico, strike the plexiglas tubes and split water, the storage tanks would fill with gas, the fuel-cell generator would turn and electricity would be ready to flow to the town in front of friends from Lordsburg, representatives of the national media, people from the power companies, colleagues from Golden and MIT, Caltech and the Lawrence Berkeley labs, as well as a few entrepreneurs from the Stanford area. A press pack, including a special glossy brochure, would be available. All this had been arranged by Hammer and his team. Under a vast marquee that he swore he had got for free from NASA, they would drink champagne, give interviews and talk about contracts. At a given signal, the Nobel laureate would throw a switch and the new era would commence.