William Pitt Gilt Metal Portrait Profile Plaque, circa 1806.A William Pitt Gilt Metal Relief Portrait Profile Roundel circa 1806, in a Square Ebonised Plaque. William Pitt the Younger (1759 1806) was a British statesman, the youngest and last Prime Minister of Great Britain from 1783 until the 1800 Acts of the Union and then first Prime Minister of the United Kingdon from 1801. He left office in March 1801, but served as prime minister again from 1804 until his death in 1806. He was known as "Pitt the Younger"