Which British king was nicknamed 'The First gentleman of Europe'?

King George IV

George IV (George Augustus Frederick; 12 August 1762 – 26 June 1830) was King of the United Kingdom of Great Britain and Ireland and of Hanover following the death of his father, George III, on 29 January 1820, until his own death ten years later. From 1811 until his accession, he served as Prince Regent during his father's final mental illness.

George IV led an extravagant lifestyle that contributed to the fashions of the Regency era. He was a patron of new forms of leisure, style and taste. He commissioned John Nash to build the Royal Pavilion in Brighton and remodel Buckingham Palace, and Sir Jeffry Wyattville to rebuild Windsor Castle.

One of George IV’s friends was Beau Brummell, the original dandy who made top hats fashionable and was known to spend hours on his toilette. So it is no surprise that the dandy’s fashion choice might have rubbed off on the king, who was known as the ‘first gentleman of Europe’