In the City of London, behind the Bank of England, there is a little street called Austin Friars. Sober and narrow, it offers glimpse of a city garden, something sweetly natural at the granite heart of the establishment. The garden belongs to Drapers’ Hall, which stands on the site of one of the great powerhouses of Tudor London. In the 1530s, Austin Friars was the home of Thomas Cromwell, who was, except for the king, the most powerful man in England. Rich, cultured, multilingual, a friend and patron of artists and scholars, he was a master of the political arts. The house was a bustling ministerial headquarters, where petitioners from all over Europe pursued the royal secretary for favours and begged for a glimpse, a word.

Cromwell was a man of property. He had apartments at court, and the Rolls House in Chancery Lane went with his job. London was small then, and his Hackney and Stepney houses stood in the fields. He had a hunting lodge in Canonbury where in summer, in his rare quiet moments, he could sit in one of the garden towers and look down on London’s treetops, contemplating the daily challenges thrown up by his master, the exacting, clever, capricious Henry VIII.

Who was he? Where did he come from? To find the answer you had to cross the bandit country west of London, to Putney, where he was born on a date unknown. The year 1485 seems to fit. It was the year of the battle of Bosworth, the year that Henry Tudor (according to legend) picked the crown of England out of a thorn bush. It’s where, for convenience, the historians begin “modern history”, sloughing off the Plantagenets, the middle ages, the old world of candlelit, Roman Catholic England, and inaugurating a new era of hard-eyed moneymen, with Cromwell leading from the front.

It wasn’t that simple, of course. The people in Putney had no idea a new era had begun. To them the triumph of the new regime must have looked like another incident in the civil war that England’s aristocrats had been fighting for a generation. No one knew the Tudors would manage to hang on to power for more than a century and reshape their country – thanks in no little part to the unremarked, unrecorded birth of the son of Walter Cromwell, the parish bully.

As the 15th century closed, Thomas was the country’s most common male name. Thomases came two a penny, and no one noticed this one until he was a teenager, and in trouble. If he went to school, nobody remembered. At some point he disappeared, possibly in dispute with the law, as his father was so frequently. Walter Cromwell was not a poor man. He ran a small brewery; he had an interest in a fulling mill and possibly a smithy. But he was the neighbour from hell. He consumed a good deal of his own beer, or (since he was routinely fined for watering his ale) perhaps someone else’s. He was violent and quarrelsome: a father worth escaping.

It is at the point of escape – the night before the 15-year-old boy is booted out of his home and his childhood – that my novel Wolf Hall opens. It begins with a beaten boy lying on cobblestones, his vision clouded by his own blood, while his father bellows down at him, “So now get up.” The trilogy – the last book is in progress – will follow Thomas Cromwell’s life from that moment – from that instant, that pulse beat, when he thinks he is going to die – to the reprise some 40 years on, when he thinks the same, and he is right: he ends on Tower Hill, looking at the executioner’s boots, an axe poised above him. The project is like a breath held. I want to know how it felt to live in the space of that breath: to begin as Walter’s no-good heir, and end as Earl of Essex.

Portrait of Thomas Cromwell by Holbein. Photograph: Alamy

About the year 1500, the young Thomas Cromwell fled England. The next few years are dark. “I was a ruffian in my youth,” was all he ever said. It seems likely he joined the French army, fighting as a mercenary, and campaigned with them in Italy. Destitute in the wake of French defeat, he joined the household of a Florentine merchant banker, perhaps as a servant; his uncle had been a cook. Agile-minded and quick to learn languages, he was promoted; facts are scant, we can only guess. Before the age of 30, he nudges on to the historical record, sighted in Venice and in Rome, in Antwerp; he is a banker, an apprentice lawyer, a broker in the wool trade. Then he comes home, to the hopeful country of the second Tudor, the young Henry VIII. Soon he is talent-spotted by Cardinal Wolsey, the king’s omnicompetent, vain and splendid minister.

Wolsey took to him. What’s not to like? The scowling asocial Cromwell is an invention of posterity, overinfluenced by Holbein’s dour portrait. His contemporaries saw easy charm and social adroitness. He was ingenious, keen to please, irreverently funny; his energy seemed inexhaustible. The writer Nicola Shulman has remarked that he lived in an element of “decelerated time”, accomplishing a week’s work in a day. He acted for the cardinal as lawyer and business adviser, and when Wolsey fell from power he transferred his services to the king and did what the cardinal couldn’t do: he freed his master from his first marriage to Katherine of Aragon, so that he could marry Anne Boleyn, the woman he believed would give him a son to secure the future of his dynasty.

The fall of Anne Boleyn is the subject of Bring Up the Bodies, my second Cromwell novel. The novel, and the TV retelling, ends with her execution. Why revisit some of the best-known events in English history? It seemed to me that at the core of the story there was something missing. There was a moving area of darkness where Cromwell ought to be. Much studied by academic historians, he appears in popular history as an all-purpose, pre-packaged villain. In fiction and drama he is just off the page or in the wings, doing something nefarious: but what? I wanted to put the spotlight on him; more than that, I wanted to get behind his eyes, the eyes of a man obscurely born, and watch as his country shapes itself about him, a dazzle of possibility.

To do that, I had to accustom my inner eye to bare underfurnished rooms, where possessions are kept in chests, and floors are strewn with rushes, and turkey carpets glow on tabletops in the houses of the wealthy. I needed to wear, in my imagination, fresh linen, heavy draping wool, damask and diamonds. My palate had to grow used to the sweet, spicy, scented tastes of Tudor cooking, to winter stockfish and summer fruit tarts. I had to live in a gated city, with green open spaces surrounding monasteries, with the long gardens of noble houses running down to the Thames: a London where the river was the main highway and there was only one bridge, sometimes decorated with severed heads. One mistake and you were finished, if you worked for Henry VIII – or if you married him.

It was once I felt comfortable in this world that I opened the door to others. The first two Cromwell novels have been adapted for the RSC by Mike Poulton. After two successful seasons they are heading for Broadway. Now a six-part series – another cast, another adapter, a completely fresh take on the material – brings the stories to the screen. People say to me, “Is it strange to see the people brought to life?” I think, but when were they ever dead?

The story of Cromwell, Henry and his wives is about power politics and religious strife, but also about shame and sexual desire and the mysterious destabilising power of femininity. In this era, women become players as never before. The figures in this drama live in our psyche. They’re part of our folklore, our mythology. You can reshape them, and choose – every writer chooses differently – how you relate to the historical facts. My own method is to wrap the fiction around the documented record, to let imagination lead us by touch into the rooms where history can’t shine a light. The truth is always best, if you can get at it. Time and again, looking at the events of Henry’s reign and Cromwell’s life, you say, “You couldn’t make it up.” Or you could, but no one would believe you.

Cromwell is a man who makes his own luck. As a boy he loses his home, his language. He rebuilds his life but his wife and daughters die, his patron Wolsey is disgraced and hounded to his grave. Damaged but not broken, Cromwell keeps climbing, agile, tenacious and without illusions; as he says in the third novel, smiling, “Every chancer has his chance with me.” He is a recognisably modern man, and we think we understand him; but the swift savagery with which he solves his problems leaves us shaking in our shoes. At the end of the story (the story so far) he has a hand on the next rung of the ladder. Soon to be Lord Cromwell, he is climbing towards the height of his power: he has four years to live, in the puzzled regard of a king who is perhaps already a little afraid of what he’s created.