According to a newly released study, high concentrations of arsenic have been found in a sample of King George III's hair, and this, say the authors, may have contributed to his unusually severe and prolonged bouts of madness.
King George III, while he was on the throne, had five major episodes of prolonged and profound mental derangement.
Originally the King's illness was thought to be a psychiatric disorder but the physical manifestations of the illness revealed the monarch suffered from acute attacks of porphyria, a genetic defect leading to the faulty synthesis of a protein.
To date however, there is little information on hand to explain the unusual persistence, severity, and late onset of attacks.
However one possible explanation is exposure to heavy metals, including lead and mercury.
Martin Warren of the University of Kent, and his colleagues investigated exposure to such metals in a sample of the King's hair.
They surprisingly found a high concentration of arsenic in the hair sample.
Then the researchers examined the Royal physician's medical notes to try and identify the source of the arsenic, and they discovered that the main compound administered to the King during his illness was emetic tartar.
Emetic tartar apparently contains a substance called antimony, which can be contaminated with arsenic, and the authors believe that the King's medication was the source of the arsenic found in the hair sample.
According to Professor Warren the presence of arsenic in the sample of the King's hair provides a perfectly sound explanation for the length and severity of his attacks of illness; and contamination of his antimonial medications is the probable source of the arsenic.
The team suggest that exposure to arsenic could very well exacerbate attacks of porphyria in a genetically predisposed individual.
The study is published in the current edition of The Lancet.