Leonard James Callaghan, Baron Callaghan of Cardiff (27 March 1912 – 26 March 2005), often known as Jim Callaghan, was a British politician who served as Prime Minister of the United Kingdom from 1976 to 1979 and Leader of the Labour Party from 1976 to 1980. To date, Callaghan is the only person to have held all four Great Offices of State, having also served as Chancellor of the Exchequer (1964–1967), Home Secretary (1967–1970) and Foreign Secretary (1974–1976), prior to his premiership. As Prime Minister, he had some successes, but is remembered chiefly for the "Winter of Discontent" of 1978–79. During a very cold winter, his battle with trade unions led to immense strikes that seriously inconvenienced the public, leading to his defeat in a general election by Conservative leader Margaret Thatcher.
Born into a working class family, Callaghan started his career at age 17 as a tax inspector, before becoming a trade union official in the 1930s; he then served in the Royal Navy during World War II. He entered the House of Commons in 1945, and was on the left wing of the party. Callaghan steadily moved towards the right of the party, but maintained his reputation as "The Keeper of the Cloth Cap" – that is, he was seen as dedicated to maintaining close ties between the Labour Party and the trade unions. Callaghan's period as Chancellor of the Exchequer coincided with a turbulent period for the British economy, during which he had to wrestle with a balance of payments deficit and speculative attacks on the pound sterling (its exchange rate to other currencies was almost fixed by the Bretton Woods system). On 18 November 1967, the government devalued the pound sterling. Callaghan became Home Secretary; he sent the British Army to support the police in Northern Ireland (NI), after a request from the NI Government.
After Labour was defeated at the 1970 general election, Callaghan played a key role in the Shadow Cabinet. He became Foreign Secretary in 1974 upon Labour regaining government, taking responsibility for renegotiating the terms of the UK's membership of the European Communities, and supporting a "Yes" vote in the 1975 referendum to remain in the EC. When Prime Minister Harold Wilson resigned in 1976, Callaghan defeated five other candidates to be elected as his replacement. Labour had already lost its narrow majority in the House of Commons by the time he became Prime Minister, and further by-election defeats and defections forced Callaghan to deal with minor parties such as the Liberal Party, particularly in the "Lib–Lab pact" of 1977–78. Industrial disputes and widespread strikes in the 1978–79 "Winter of Discontent" made Callaghan's government unpopular, and the defeat of the referendum on devolution for Scotland led to the successful passage of a motion of no-confidence on 28 March 1979. This was followed by a defeat at the ensuing general election.
Callaghan continued as Labour Party leader until November 1980, and campaigned to reform the process by which the party elected its leader, before returning to the backbenches where he remained until he was made a life peer as Baron Callaghan of Cardiff. He went on to live longer than any other British prime minister in history (92 years and 364 days).