IN 1759, the year before George III began his long reign, thousands of people in the West Country were afflicted with a mysterious ailment whose symptoms included severe abdominal pain and mental confusion. The cause of the epidemic was finally traced by a young physician, George Baker, to the contamination of the local cider by lead from the apple presses. A dangerous consequence of lead poisoning, also known as plumbism, is the disruption of the body's ability to make the red pigment (haem) in blood. In this way, lead poisoning can cause a form of porphyria. The symptoms of this can be severe and may include muscular weakness, skin rashes and the production of dark red, purple or even blackish urine in addition to terrible abdominal pain and temporary mental disorientation.
Dr Baker was able to relieve the suffering caused by the Devonshire colic by recommending abstention from the local tipple. Less fortunate are those suffering from an inherited form of porphyria who are prone to periodic attacks of the illness. Even today there is no known cure.
Porphyria was not classified as a distinct medical disorder until the early 20th century, but Dr Baker was soon to find himself in charge of history's most famous porphyria patient. In recognition of his talents, he was knighted and appointed head of George III's medical staff. In this position, he was faced with the familiar symptoms of acute abdominal pain and mental confusion in the sovereign himself. One can only assume that it was the King's additional symptoms - racing pulse, insomnia, general malaise and discoloured excrement - which obscured the similarity between his ailment and the 1759 Devonshire epidemic; Baker recorded that he had never seen anything like the King's symptoms before.
It was not until the 1960s that the hypothesis was advanced that George III, instead of suffering from some indeterminate "madness", was actually porphyric. …