British statesman, born in Dublin, Ireland. He studied at Cambridge, and became Whig MP for Co Down (1790), turning Tory in 1795. He was created Viscount Castlereagh in 1796, and became Irish secretary (1797), President of the Board of Control (1802), and minister of war (1805–6, 1807–9). His major achievements date from 1812, when, as foreign secretary under Lord Liverpool, he was at the heart of the coalition against Napoleon (1813–14). He represented England at Chaumont and Vienna (1814–15), Paris (1815), and Aix-la-Chapelle (1818). He advocated ‘Congress diplomacy’ among the great powers, to avoid further warfare. Believing that he was being blackmailed for homosexuality, he committed suicide at Foots Cray, his Kentish seat.