Very near the Bank of England, at the foot of the glass cliff of Tower 42, there is a secret city garden that now belongs to Draper’s Hall. A plaque on the wall says: “On this site, once part of the Augustinian Priory, Thomas Cromwell built his palace and in 1536 plotted the downfall of Anne Boleyn, second wife of Henry VIII.”

“Palace” is perhaps an inflation. The building at Austin Friars was an opulent merchant’s house, which from 1530 accreted new wings, storerooms, strongrooms, and tighter and tighter security. It was a powerhouse of Tudor politics, and over a decade, its master became one of the richest and most powerful men in England: councillor and secretary to the king, Master of the Rolls, Lord Privy Seal and eventually Earl of Essex. Austin Friars was not a quiet spot. Twice a day, 200 of London’s poor swarmed to the gate to be fed by the great man’s kitchen. The alleys and courts shivered with the sound of churches’ bells, and from the priory drifted, mingled with Latin chants, the sound of the friars’ supper parties; they lived very well, and were on good terms with their worldly neighbour. In the streets you would hear as much Flemish and Spanish as English. This was a cosmopolitan corner of the city, where the multilingual Cromwell was right at home.

Every day of Cromwell’s political life was a fight — not just because of what he stood for, but because of who he was. He came from a humble background, and historians as well as contemporaries seem to have held that against him. He is accused of hounding to his death the saintly Thomas More — though from our perspective, the heretic-hunting More doesn’t look so saintly, and it was the king, not Cromwell, who wanted More dead. In novels, and in plays and films such as A Man for All Seasons, Cromwell is a cold Machiavellian, or a desiccated administrator. His character has been painted as so comprehensively black that any reasonable person would think — as I did — that there must be another side to the story.

My novel Wolf Hall sets out to imagine his childhood, explore his early life and chronicle his rise to power. In a second book, I mean to take his story through to 1540, the year in which, like many of Henry’s able and loyal servants, he faced the executioner. When I set out to find Cromwell, I discovered a man who succeeded by toughness and unremitting hard work, by ingenuity, suppleness and flair; a gregarious man, generous and cultured, good at making friends and watchful of their interests. There was a touch of the mafia boss about him: once you were part of the Austin Friars family, you would be protected, made useful and often made rich. He had a strong sense of purpose and an armoured self-belief. I was enthralled by watching his acute political instinct in operation as he picked his way from crisis to crisis, and puzzled by a man who seemed capable of both great personal kindness and utter ruthlessness.

There are usually at least two ways to read a communication from the dead. In Cromwell’s case, many scholars choose to put the worst construction on every piece of documentary evidence left to us. The historian Geoffrey Elton was emphatic about Cromwell’s status and importance: “Wherever one touches him, one finds originality and the unconventional.” But as many of today’s Tudor historians were trained by Elton, they have to define themselves against him: Cromwell at the moment is out of fashion, and his biographies tend to rehash old clichés and prejudices. They say “Thomas Cromwell” on the cover, but there isn't a man inside. The flesh-and-blood reality is elusive. His fingerprints are all over the laws and public acts of Henry’s reign. His private life is largely hidden.

It seemed to me there was a challenge. There might not be the personal material for a good biography. But could a novelist reconstruct him, by applying an informed imagination? For the decade of his power, the papers of the reign — the historian’s basic source — are almost a history of Cromwell. Luckily, he filed almost every letter ever sent to him. What sort of a man did they think they were writing to, these correspondents from all over Europe? I saw him, initially, through the mirror of other people’s perceptions. Then I tried — because this is what a novelist can do — to step through the glass and see the Tudor world from behind his eyes.

He was born in Putney c1485, the first year of the Tudor dynasty. His father, Walter, was a small-time businessman and small-time crook; he had a blacksmith’s shop, an interest in a fulling mill and a brewery notorious for bad beer. Walter was a drunk, and violent. Aged about 15, Thomas ran away, crossed the Channel and joined the French army. Later it was said he had been in trouble with the law. His only comment was: “I was a ruffian in my youth.” Throughout his career, people told lurid stories about where he’d been, whom he’d met, what he knew, the terrible things he had done. He never troubled to contradict them. If, when you looked at him, you frightened yourself, that suited him down to the ground.

After parting company with the French, Cromwell was sighted in Venice, in Florence and in Rome, clerking for merchant bankers; later he was spotted in the Netherlands, trading at one of the big wool markets. We don’t know where he picked up his education, but he had a daunting intellect and a formidable memory. His contemporaries believed he had learnt the New Testament by heart; this may, of course, have been one of his bluffs. In his late twenties, he came back to London, married a well-off wool-trade widow and set himself up as a lawyer. He and Elizabeth had a son, Gregory, and two daughters, Grace and Anne, but the girls died young, and so did his wife. He never remarried. Too busy, probably; but, then, if you worked for Henry VIII, you probably felt that at the end of the day you needed a break from wives.

In 1523, Cromwell became an MP. At about that time he was talent-spotted by Thomas Wolsey, England’s cardinal and lord chancellor, the brilliant, flamboyant, charismatic man who was the country’s alter rex: the other king. They became close friends; he was Wolsey’s “entirely beloved Cromwell”. In the dark days of Wolsey’s fall, one of the cardinal’s servants, George Cavendish, came across a spectacle that dismayed him: Cromwell, leafing through a prayer book and crying. It was a sight never seen again. He was not given to the open display of emotion, and we will never really understand his religious position. Some historians take him to be a cynic who used religion as an instrument of policy, though it was he who put the English Bible in every church. I take his reformist convictions to be sincere. But you needed a sense of irony to work with him. The Spanish ambassador described how one day, when spinning him a particularly unlikely line about the king, the minister simply burst out laughing.

Cromwell was so identified with Wolsey that the cardinal’s death should have been a disaster. But Henry seldom acted by strict logic, and it was the fact that Cromwell had stuck by his master that made him covet such loyalty for himself. For years Henry had been trying to disentangle himself from his long marriage to Catherine of Aragon and free himself to marry Anne Boleyn, with whom he was infatuated and who he hoped would give him a son. He had succeeded in scandalising and dividing Europe, but not in getting his divorce. Cromwell helped him cut through the knot. After England’s break with Rome, nobody was closer to the king.

Holbein’s portrait of Cromwell dates from about this time. He is a grim presence, pushed into a small space, as if only by wedging him between two tables could the painter keep him from pounding off to get on with his day. He was, one of his friends said tactfully, “inclined to be fat”, but he must have been a very fit man to have shouldered his workload. In conversation, the Spanish ambassador said, Cromwell was animated and witty. His eyes were always on your face; he read you like a book.

Henry made Cromwell his deputy for the administration of his new Church of England, and put him in charge of freeing up the immense wealth of England’s monasteries and diverting it into the crown’s pocket. Henry was good at spending money, and Cromwell was good at making it. He costed out Henry’s whims and made them reality. But political outcomes are hard to calculate, and Cromwell was a gambler who took huge risks — particularly when the king handed him the job of getting rid of his second wife. He saw Anne Boleyn in, and saw her out, orchestrating an elaborate plot in which warring factions agreed to work together, each thinking they would come out on top; in the end, the winner was Cromwell. When Jane Seymour became queen, Cromwell married his son, Gregory, to her sister. The blacksmith’s boy, the runaway from Putney, had succeeded in becoming very nearly royal himself.

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