In 1545, the year in which he turned seventy, Michelangelo Buonarroti completed his last public sculpture, the tomb of Pope Julius II in the church of San Pietro in Vincoli, Rome. Others might have settled into a well-deserved retirement, looking back on a triumphant career. Not Michelangelo, who went on to spend the best part of the next two decades fixing a disastrous building project at St Peter’s in Rome and designing the dome that now dominates the city’s skyline.

Born in 1475, Michelangelo spent much of his early career in Florence, enjoying the patronage of both the Medici family and their republican rivals. There he produced such works as his celebrated David (for the latter) and the new sacristy at the basilica of San Lorenzo (for the former). He also worked in Rome, where in 1512 he completed the Sistine Chapel ceiling. It was to Rome that he returned in the 1530s, disillusioned with the new ducal regime that had replaced the republican government in Florence. The popes were hardly more democratic, but the curia provided ample artistic opportunities, among them the commission for The Last Judgment on the wall of the Sistine Chapel.

Michelangelo became chief architect at St Peter’s in 1546, following the death of Antonio da Sangallo, who had served for twenty years in the same position. Sangallo had not been the first to occupy that role: the project was already decades old when he took over. In the early years of the 16th century, Pope Julius II had initiated renovations when it became clear that the ancient basilica, completed around AD 360 on the site believed to be St Peter’s tomb, was at serious risk of collapse. At first, almost no one proposed remaking it entirely. The new St Peter’s took shape slowly, and for all its spiritual symbolism it was the architectural project from hell. Imagine a century of Grand Designs specials with one pope after another playing the despairing client and you get the picture.

Michelangelo’s appointment at the age of seventy-one proved controversial with the existing staff. ‘Just as the artist feared,’ William E Wallace writes, ‘he inherited a bevy of thickheaded deputies, a bunch of obstructionist overseers, and a recalcitrant workforce.’ Sangallo’s model looked great in miniature, but creating it in full size had proved an engineering nightmare. Michelangelo had to convince his workers to undo substantial elements of the earlier construction so that he could address structural problems in the crossing vaults. He also had to abandon a scheme for an exterior ambulatory that would only have exacerbated the design flaws and reduced the amount of light inside the church. Wallace brilliantly evokes the day-to-day life of the project as Michelangelo struggled to resolve its many difficulties, which included dealing with the mechanics of the building operation, the calculations of the amount of travertine required, the quarrymen at Tivoli and the practicalities of transport.

Wallace has Michelangelo down as a ‘micromanaging, type-A personality’, though by the time he came to work on St Peter’s, the artist’s age, health and commitment to multiple projects, such as Pope Paul III’s Palazzo Farnese, had forced him to make some compromises in his working practices. Such was Michelangelo’s celebrity that his name alone conferred prestige on a project, and successive popes demanded his involvement in their pet initiatives. As a consequence, in these later years his creative efforts shifted. He made fewer individual works (though there were still some, notably two pietà sculptures, and frescoes in the Pauline Chapel) and instead focused on drawings and designs, producing concepts that could be carried through by others. Although Michelangelo did not live to see St Peter’s finished – in fact, he was involved in the reconstruction project for only 12 per cent of its total duration – Wallace makes an emphatic case for the significance of his input.

What the dome meant at the end of Michelangelo’s life was very different from what it meant at the start. Between Julius II’s initial decision to begin renovation work at St Peter’s and the basilica’s completion, western Christendom had split. At the beginning of the 16th century, St Peter’s was the symbol of a single apostolic succession of popes (albeit with a few antipopes along the way). At the end, it was the symbol of a revived Roman Catholic Church that had, after many delays, seen through its own reform process to compete with the Protestant challenge. Michelangelo’s work on the basilica coincided with the deliberations of the Council of Trent, the body assembled on a series of occasions between 1545 and 1563 to debate the Church’s response to Protestantism. While this wider Counter-Reformation context doesn’t get a great deal of attention in the book, we do hear of Michelangelo’s ties to a group of radical religious reformers. Known as the Spirituali, these individuals emphasised the importance of faith in Christ in achieving human salvation, an idea more often associated with Protestantism. Their most important text was The Benefit of Christ Crucified, a work banned by the Church as heretical, which Wallace imagines Michelangelo reading in a week in 1557. Michelangelo himself, so far as we can tell, responded to the persecution of the Spirituali with a self-imposed silence about his own beliefs in the later years of his life.

Just as problematic for ‘God’s architect’ was the question of his private life. Although Wallace’s primary focus is on Michelangelo at work, he paints a picture too of the artist at home, whether at prayer, corresponding with family members or enduring the pain of kidney stones. His was not the archetypal household of its time and place: Michelangelo was unmarried and did not live with blood relatives. Nor does it fit the model of the characteristic male-dominated ecclesiastical house in Rome, for the simple reason that Michelangelo was not a cleric. There was, in fact, a great deal of the ‘found family’ about it: a motley bunch of ‘housemates’ (Wallace’s term) shared the same space, in some cases with their spouses, sometimes for business convenience, sometimes for more personal reasons.

Thanks to Gary Ferguson’s recent account of Renaissance Rome’s queer subculture, we now have more information with which to flesh out the might-have-beens of same-sex relationships at that time. But while elsewhere in the book Wallace is happy to fill in historical gaps with speculation, he opts for studied ambiguity when it comes to the precise nature of Michelangelo’s friendships with other men. In his later years, Michelangelo had a long-term relationship with Tommaso dei Cavalieri, who was at his deathbed. As Wallace explains, this ‘matured – mellowing from its initial passionate intensity – and continued for more than thirty years’. He was close to other men too, among them Ludovico Beccadelli, ‘one of those rare friends who shared completely Michelangelo’s contradictory feelings of carnal desire and spiritual yearning’. Beccadelli described himself as ‘in exile’ so far as ‘matters of the flesh’ were concerned. Whether or not one accepts that as the whole truth, it was a prudent thing to say in Counter-Reformation Rome.

Indeed, in his later life, Michelangelo was deeply concerned with his own salvation, seeing his work at St Peter’s as central to it. When Giorgio Vasari came to update his Lives of the Artists in 1568, four years after Michelangelo’s death, he observed that ‘God, who looks after good men, favoured Michelangelo during his lifetime and never ceased to protect both him and St Peter’s’. While two decades earlier the orthodoxy of Michelangelo’s Last Judgment had been questioned, he was now truly ‘God’s architect’.