1792 German States 4 Pfenning 4pf KM-398 Grades vg+. George III (George William Frederick; 4 June 1738–29 January 1820) was King of Great Britain and of Ireland from 25 October 1760 until the union of the two kingdoms on 1 January 1801, after which he was King of the United Kingdom of Great Britain and Ireland until his death in 1820. He was concurrently Duke and Prince-elector of Brunswick-Lüneburg ("Hanover") in the Holy Roman Empire before becoming King of Hanover on 12 October 1814. He was a monarch of the House of Hanover but, unlike his two predecessors, he was born in Great Britain, spoke English as his first language and never visited Hanover.In the later part of his life, George had recurrent, and eventually permanent, mental illness. Although it has since been suggested that he had bipolar disorder or the blood disease porphyria, the cause of his illness remains unknown. George suffered a final relapse in 1810, and his eldest son, the Prince of Wales, became Prince Regent the following year. When George III died in 1820, the Regent succeeded him as King George IV.