The theory was constructed in the 19th century, as part of a narrative that showed Henry as a sexual beast justly punished for his promiscuity

Yet clearly he was able to make his wives pregnant. Was something else wrong? The old notion that Henry had syphilis has been discarded. There never was any contemporary evidence for it. He had few mistresses compared to other grandees of his time. I think it was more important to him to be good, to be seen to be good, than to be gratified in this particular way. In fact I think we can say that the old monster was a bit of a romantic.

Later in life, when he married Anne of Cleves, he didn’t want to have sex with a woman with whom he wasn’t in love; it was a scruple that baffled his contemporaries

Recently a new hypothesis about Henry has emerged. In 2010 a paper by Catrina Banks Whitley and Kyra Cornelius Kramer appeared in the Historical Journal, called ‘A New Explanation of the Reproductive Woes and Midlife Decline of Henry VIII’. It suggested that Henry had a blood type called Kells positive. People who are Kells positive carry an extra antibody on the surface of their red blood cells. The blood type is rare, so we can assume Henry’s wives were Kells negative, and that their lack of compatibility was the reason for the multiple reproductive failures. When a woman who is Kells negative conceives by a man who is Kells positive, she will, if the foetus itself is Kells positive, become sensitised; her immune system will try to reject the foetus. The first pregnancy will go well, other things being equal. As with rhesus incompatibility, it takes one pregnancy for the woman to develop the sensitisation. But later children will die before or just after birth.

To a certain point this fits Henry’s story.