Then he spoke of Areopagitica and its relevance to modern politics. At this she stopped on the path and asked significantly what a scientist was doing knowing so much about Milton, and he thought he had been rumbled. He pretended to be just a little insulted. All knowledge interested him, he said, the demarcations between subjects were mere conveniences, or historical accidents, or the inertia of tradition. To illustrate his point, he drew on scraps he had picked up from his anthropologist and zoologist friends. With a first touch of warmth in her voice, she began to ask him questions about himself, though she did not care to hear about physics. And where was he from? Essex, he said. But so was she! From Chingford! That was his lucky break and he seized his chance. He asked her to dinner. She said yes.

He was to count that misty, sunny November afternoon, along the Cherwell river by the Rainbow Bridge, as the point at which the first of his marriages began. Three days later he took her to dinner at the Randolph Hotel, and by then had completed another whole day of Milton. It was already clear that his own special study would be light, and he was naturally drawn to the poem of that name, and learned its last dozen lines by heart, and over the second bottle of wine talked to her of its pathos, a blind man lamenting what he would never see, then celebrating the redeeming power of the imagination. Over the starched tablecloth, wine glass in hand, he recited it to her, ending '…thou Celestial light / Shine inward, and the mind through all her powers / Irradiate, there plant eyes, all mist from thence / Purge and disperse, that I may see and tell / Of things invisible to mortal sight'. At these lines he saw the tears well in Maisie's eyes, and reached under his chair to produce his gift, Areopagitica, bound in calf leather in 1738. She was stunned. A week later, illicitly in her room, to the sound of Sergeant Pepper playing on the Dansette record player he had repaired for her that afternoon with smoking soldering iron, they were lovers at last. The term 'dirty girl', with its suggestion that she was general property, was now obnoxious to him. Still, she was far bolder and wilder, more experimental and generous in love-making than any girl he had known. She also cooked a fine steak and kidney pie. He decided he was in love.

Going after Maisie was a relentless, highly organised pursuit, and it gave him great satisfaction, and it was a turning point in his development, for he knew that no third-year arts person, however bright, could have passed himself off, after a week's study, among the undergraduate mathematicians and physicists who were Beard's colleagues. The traffic was one-way. His Milton week made him suspect a monstrous bluff. The reading was a slog, but he encountered nothing that could remotely be construed as an intellectual challenge, nothing on the scale of difficulty he encountered daily in his course. That very week of the Randolph dinner, he had studied the Ricci scalar and finally understood its use in general relativity. At last he thought he could grasp these extraordinary equations. The Theory was no longer an abstraction, it was sensual, he could feel the way the seamless fabric of space-time might be warped by matter, and how this fabric influenced the movement of objects, how gravity was conjured by its curvature. He could spend half an hour staring at the handful of terms and subscripts of the crux of the field equations and understand why Einstein himself had spoken of its 'incomparable beauty' and why Max Born had said it was 'the greatest feat of human thinking about nature'.

This understanding was the mental equivalent of lifting very heavy weights – not possible at first attempt. He and his lot were at lectures and lab work nine till five every day, attempting to come to terms with some of the hardest things ever thought. The arts people fell out of bed at midday for their two tutorials a week. He suspected there was nothing they talked about there that anyone with half a brain could fail to understand. He had read four of the best essays on Milton. He knew. And yet they passed themselves off as his superiors, these lie-a-beds, and he had let them intimidate him. No longer. From the moment he won Maisie, he was intellectually free.

Many years later, Beard told this story and his conclusions to an English professor in Hong Kong who said, 'But Michael, you've missed the point. If you had seduced ninety girls with ninety poets, one a week in a course of three academic years, and remembered them all at the end, the poets, I mean, and synthesised your reading into some kind of aesthetic overview, then you would have earned yourself a degree in English literature. But don't pretend that it's easy.'

But it seemed so at the time, and he was far happier during his final year, and so was Maisie. She persuaded him to grow his hair, to wear jeans instead of flannels, and to stop repairing things. It wasn't cool. And they became cool, even though they were both rather short. He gave up Park Town and found a tiny flat in Jericho, where they set up together. Her friends, all literature and history students, became his. They were wittier than his other friends, and lazier of course, and had a developed sense of pleasure, as though they felt they were owed. He cultivated new opinions – on the distribution of wealth, Vietnam, the events in Paris, the coming revolution, and LSD, which he declared to be extremely important, though he refused to take it himself. When he heard himself sounding off, he was not at all convinced, and was amazed that no one took him for a fraud. He tried pot and disliked it intensely for the way it interfered with his memory. Despite the usual parties, with howling music and terrible wine in sodden paper cups, he and Maisie never stopped working. Summer came, and finals, and then, to their stupid surprise, it was all over and everyone dispersed.

They both got firsts. Michael was offered the place he wanted at the University of Sussex to do a PhD. They went to Brighton together and found a fine place to live from September, an old rectory in an outlying village on the Sussex Downs. The rent was beyond them and so, before returning to Oxford, they agreed to share with a couple studying theology who had newborn identical twins. The Chingford newspaper ran a story about the local working-class girl who 'soared to the heights', and it was from these heights, and to hold together their disintegrating milieu, that they decided to get married, not because it was the conventional thing to do, but precisely because it was the opposite, it was exotic, it was hilarious and camp and harmlessly old-fashioned, like the tasselled military uniforms the Beatles wore in promotional pictures for their sensational LP. For that reason, the couple did not invite or even inform their parents. They were married in the Oxford registry office, and got drunk on Port Meadow with a handful of friends who came for the day. Lieutenant Colonel (rtd) Henry Beard, DSO, living alone in the old house at Cold Norton, did not learn of his son's marriage until after the divorce.

His son was thinking of that time now, forty-one years later, as he waited, jet-lagged at 5 p.m., in the circular bar of the Camino Real hotel in El Paso, Texas, for Toby Hammer to appear. The waitress came by again and Beard ordered another scotch and a second bowl of salted nuts. Under the high, stained-glass cupola, American and Mexican voices echoed and merged and he overheard no one's conversation. He was thinking of that time, the way one does on long journeys when rootlessness and boredom, lack of sleep or routine can summon from out of nowhere random stretches of the past, make them as real as a haunting. And he was almost there now, here, in the dining room of the Randolph, in suit and tie, and the white shirt he had ineptly ironed himself. After a drink he could still bring back fragments of Milton's 'Light' – 'and ever-during dark / Surrounds me, from the cheerful ways of men' and something something 'and wisdom at one entrance quite shut out'. He used a poem to get a girl, and she was gone, two years dead from cancer of the liver, in fact. But he had never shaken off the poem. He was thinking how he never took Maisie to meet his father, and never invited the old man to stay at the handsome rectory in Sussex, just left him to his sorrow while the new age dawned and the arrogant, shameless, spoiled generation turned its backs on the fathers who fought the war, dismissing them for their short hair and tidy ways and indifference to rock and roll.