Many other doctors would have thought their luck had run out. Jamaica, won from the Spanish by Oliver Cromwell’s navy, was a rackety place, much-visited by pirates, with a coarse-living, hard-drinking planter class; mortality from tropical illnesses (and alcohol) was high. But for Sloane it was a dream come true: he could collect specimens of unknown species of plants, shells, insects and other animals, and gather all kinds of other information, too.

When, after less than a year, the Duke died – from a combination, it seems, of tropical disease and claret – Sloane’s first duty was to supervise the eviscerating and embalming of his corpse, a process Delbourgo describes in stomach-churning detail. But on the voyage back to England the ducal coffin was accompanied by crates of specimens, many volumes of pressed dried plants, an iguana (which unfortunately jumped overboard) and an affectionate seven-foot-long yellow snake, which, Sloane wrote, “followed me as a dog would his master”.  (One day, alas, instead of following him, it found its way to the Duchess’s quarters, where her terrified servants shot it dead.)