Leonard James Callaghan, Baron Callaghan of Cardiff ( ; 27 March 191226 March 2005), was a British statesman who served as Prime Minister of the United Kingdom from 1976 to 1979 and Leader of the Labour Party from 1976 to 1980. Callaghan is the only person to have held all four Great Offices of State, having also served as Chancellor of the Exchequer