The English king Georg III (1738-1820) was a dutiful sovereign, a loving family man, a good rider and sportsman, temperate in drink and food, refusing the orgies of his contemporaries. He patronized science and was a dedicated collector of book and pictures. In spite of his healthy living he four times after the age of 50 suffered from periods of illness, causing political crises. His symptoms were confusion, pains and discoloured urine. Each time he completely recovered after 3-4 months. These enigmatic fits have now been diagnosed as porphyria. Reference is given to the outstanding research by Swedish scientists regarding this disease.