"Maist" [Mace-t] Meaning: Most
Along with William Pitt the Younger, the Prime Minister, Castlereagh, the Chief Secretary for Ireland, was the principal architect of the British-Irish Union of 1801. At the War Office he radically reformed the British army and, against stern opposition, advanced the career of the future Duke of Wellington. Between 1812 and 1822 Castlereagh was British Foreign Secretary. He constructed the great coalitions which ultimately defeated Napoleon. At the Congress of Vienna he helped redraw the map of Europe in such a way as to lay the foundations of one of the longest periods of peace in modern European history.
Further reading: Wendy Hinde, Castlereagh (London, 1981).