Thomas Cromwell is one of the most famous - or notorious - figures in English history.

Born in obscurity in Putney, he became a fixer for Cardinal Wolsey in the 1520s and remained intensely loyal to his memory even when Wolsey had fallen for failing to solve Henry VIII's 'Great Matter' - lack of a male heir and efforts to repudiate his wife Katherine of Aragon. Henry too appreciated Cromwell's talent and promoted him to a series of ever greater offices, such that in the 1530s he was effectively running the country for the King.

That decade was one of the most momentous in English history: it saw a religious break with the Pope, unprecedented use of parliament, the dissolution of all monasteries, and the coming of the Protestantism which decisively shaped the future of this country. Cromwell was central to all this, but establishing his role with precision, at a distance of nearly 500 years and after the destruction of many of his papers at his own fall, has been notoriously difficult.

Diarmaid MacCulloch's biography is much the most complete and persuasive life ever written of this elusive figure, a masterclass in historical detective work, making connections not previously seen. It draws together national and international events, and reveals the channels through which so much of power in early Tudor England flowed. It overturns many received interpretations, for example that Cromwell and Anne Boleyn were allies because of their common religious sympathies, showing how he in fact destroyed her; or that Cromwell was a cynical, 'secular' politician without deep-felt religious commitment. It introduces the many different personalities contributing to these foundational years, all worrying about what MacCulloch calls the 'terrifyingly unpredictable' Henry VIII, and shows how things could easily have turned out differently. MacCulloch's familiarity with the 1520s and 1530s allows readers to feel that they are immersed in all this, that it is going on around them.

For a time, the self-made 'ruffian', as he described himself - ruthless, adept in the exercise of power, quietly determined in religious revolution - was master of events. MacCulloch's biography for the first time reveals his true place in the making of modern England and Ireland, for good and ill.