It arrived with the army of England’s new king. Just days earlier, tens of thousands of men had been fighting for their lives on a marshy field in Bosworth, Leicestershire. There, in the summer of 1485, the bitter rivalry between Henry Tudor and Richard III was finally resolved – with Richard III dying at the Battle of Bosworth Field.

Freshly styled as Henry VII, the victor led his troops on to London. Little did he know that there they would be about to face a very different kind of mortal peril.

The first sign was a feeling of general apprehension, which soon led to shivers, pains, and headaches. Then the perspiration set in. The victims would be swamped by a torrent of sweat, which led to insatiable thirst and delirium. Finally, they’d feel an overwhelming urge to sleep. If they succumbed, they’d likely end up dead. The fatality rate was up to 50%.

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The army had brought with them a strange and unknown disease. Dubbed “The English Sweat”, this alarming malady swept across the city, killing 15,000 people in just six weeks. Eventually the epidemic fizzled out, but not before it had spread to Europe, leaving plenty of mourners in its wake.

And it kept coming back – the disease’s reign of terror continued through the next generation of Tudors, striking four more times over the coming century.

Henry VII’s son, Henry VIII, was petrified. During one particularly devastating outbreak, he slept in a different bed every night, presumably hoping to outmanoeuvre it. Here was a disease that could strike out of nowhere, often leading to death in a matter of hours; one chronicler wrote that you could be “merry at dinner and dedde [sic] at supper”. Even more uneasily, it seemed to have a peculiar affinity for the nobility. It killed many people at court, and nearly cut short the King’s romance with Anne Boleyn.