Leonard James Callaghan, Baron Callaghan of Cardiff (/ˈkæləhæn/ KAL-ə-han; 27 March 1912 – 26 March 2005), was a British statesman and Labour Party politician 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 from 1964 to 1967, Home Secretary from 1967 to 1970 and Foreign Secretary from 1974 to 1976. He was a Member of Parliament (MP) from 1945 to 1987.
Born into a working-class family in Portsmouth, Callaghan left school early and began his career as a tax inspector, before becoming a trade union official in the 1930s. He served as a lieutenant in the Royal Navy during the Second World War. He was elected to Parliament at the 1945 election, and was then regarded as being on the left wing of the Labour Party. He was appointed to the Attlee government as a parliamentary secretary in 1947, and began to move increasingly towards the right wing of the Labour Party, while maintaining his reputation as a "Keeper of the Cloth Cap" – that is, seen as maintaining close ties between Labour and the trade unions. Following Labour's defeat at the 1951 election, Callaghan increasingly became regarded as a leader of the right wing of the Labour Party, and stood for the positions of deputy leader in 1960 and for leader in 1963, but was defeated by George Brown for the former and Harold Wilson for the latter.