Henry Addington, 1st Viscount Sidmouth

Addington rose through the House of Commons, serving as Speaker from 1789 to 1801 before becoming prime minister that same year. His signature achievement was the Treaty of Amiens in 1802, an unfavorable peace with Napoleonic France that ended the Second Coalition during the French Revolutionary Wars. When the treaty broke down, he resumed hostilities without allies, conducting what amounted to weak defensive operations ahead of the War of the Third Coalition. Forced out in 1804 in favor of William Pitt the Younger - the man he'd replaced - Addington later returned as Home Secretary from 1812 to 1822, a reactionary decade spent cracking down on democratic reform advocates. He remains the longest continuously serving Home Secretary since the office was created in 1782, and died in 1844 at eighty-six.