It was also alleged that a ‘Whiskey Ring’ of government agents, including the president’s private secretary, colluded with distillers to divert tax revenues – a charge given added colour by Grant’s personal struggle with alcoholism. Most alarmingly, he served as an unwitting ally of two Wall Street buccaneers in their daring but unsuccessful attempt to corner the gold market. Specifically, it is said that by putting his trust in unqualified and self-serving subordinates, including former military associates and members of his wife’s family, he left his administration prey to corruption. This re-evaluation has to be seen in the context of a long charge sheet of indictments, above all that Grant, the boldest, most dynamic of Civil War military commanders (one whom Abraham Lincoln valued as the Union bulldog who would never shirk a fight), proved disconcertingly passive, even naive, as a political leader. After a century’s disparagement by snobbish critics such as Henry Adams, who thought him commonplace (‘the progress of evolution from President Washington to President Grant’, the Bostonian wrote, ‘was alone evidence enough to upset Darwin’), the 18th president has found increasing favour, rising from bottom place in 1948 to a position now comfortably in the top half of the rankings. In recent years, no case of advance has been more striking than that of Ulysses S Grant, a two-term president who served from 1869 to 1877. Currently, even those who have long occupied the lowest places are on the move, since the 45th president, Donald J Trump, lifts all boats: the lamentable Civil War-era presidents James Buchanan and Andrew Johnson are each likely to rise a place, and so too the egregious Warren G Harding, who presided over a notoriously corrupt administration in the early 1920s. Part of the fun is watching reputations rise and fall over time.

The ranking of American presidents by historians and political scientists is a much-loved exercise.

Grant by Ron Chernow