who was known as the mad king of england
George III of the United Kingdom In the later part of his life, George III had recurrent, and eventually permanent, mental illness. Although it has since been suggested that he had the blood disease porphyria, the cause of his illness remains unknown. After a final relapse in 1810, a regency was established, and George III's eldest son, George, Prince of Wales, ruled as Prince Regent. On George III's death, the Prince Regent succeeded his father as George IV.