It has been one hundred years since the publication of John Beresford’s The Godfather of Downing Street: Sir George Downing 1623–1684. In that time, history has not been kind to Downing. Might now be the moment to rescue his reputation? Dennis Sewell begins his new biography of the 17th-century diplomat and reformer by calling his subject a ‘liar, blackmailer, seducer and thief … a double-dealing shapeshifter [who] would betray both friends and principles without a moment’s misgiving’. One gets the feeling that Turncoat is not an attempt at rehabilitation.

Downing was born in Dublin in 1623 and raised in London; he left with his parents for New England in 1638, part of the Great Migration of Puritans that took place between 1620 and 1640. He was well connected: his uncle on his mother’s side was John Winthrop, the second governor of the Massachusetts Bay Colony, and it was apparently at his invitation that the family went over. They settled in Salem, where their minister was another relation, the charismatic preacher and ardent republican Hugh Peter, who later met a sticky end for his involvement in the trial and execution of Charles I.

In 1642, Downing was in the first class to graduate from Harvard College, an institution still reeling from the scandal of the master’s wife allegedly bulking up the hasty pudding with goats’ dung. He might have been expected to settle in New England, but when Charles I raised his standard