King George III (1738–1820) suffered from bouts of mental illness during his 60-year reign. Today many believe that he was ill with porphyria, a metabolic disorder that results in excessive amounts of porphyrins (a basic substance in body tissue, blood, and urine). He ascended the throne in 1760, upon the death of his grandfather, King George II (1683–1760). Five years later he suffered his first attack of mental illness; others followed in 1788 and 1789 and in 1803 and 1804. A final—and devastating—attack came in 1811; it left him deranged and blind.

As the popular play and movie The Madness of King George attests, the monarch’s illness presented England with a difficult problem: What do you do when a ruler becomes irrational? When the king became ill in 1788, his prime minister, William Pitt the Younger (1759–1806), and the queen ran the government, dutifully protecting the king’s interests—even while the king’s son George, the Prince of Wales (1762–1830), openly associated with his father’s parliamentary opposition and himself plotted to take control. Once King George III had recovered (in 1789), he reduced his official activities and grew increasingly reliant on Pitt, who proved to be an effective national leader. Pitt resigned in 1801 and was replaced by Henry Addington (1757–1844) until 1804 when the king, feeling that invasion by France was imminent, asked Pitt to prepare a new government. Pitt again assumed the role of prime minister, a role he retained until his death in 1806. Thereafter a coalition government, sometimes called the All-the-Talents administration, was headed by William Grenville (1759–1834) until 1807. Following that, the Duke of Portland (William Henry Bentinck; 1738–1809) became prime minister, until his death in 1809. That year, King George III participated in forming a new government for the last time. After 1811 the Prince of Wales (who would become King George IV) ruled the country as regent.

Despite his health problems King George III led England during one of the most crucial and trying periods in British history. His reign saw the American colonies fight for and win independence from Britain; the French Revolution challenge and oust royal authority in a neighboring country; Britain challenged by Napoleon’s Grand Army; and the dawning of the Industrial Revolution. Further, Ireland was brought under England by the 1801 Act of Union, forming the United Kingdom.