Leonard James "Jim" Callaghan, Baron Callaghan of Cardiff, KG, PC (27 March 1912 – 26 March 2005) was a British politician who served as the Prime Minister of the United Kingdom from 1976 to 1979 and the Leader of the Labour Party from 1976 to 1980.

Callaghan was the first and to date the only politician in history to have served in all four of the "Great Offices of State", having been Chancellor of the Exchequer from 1964 to 1967, Home Secretary from 1967 to 1970, and Foreign Secretary from 1974, until his appointment as Prime Minister in 1976.

As Prime Minister, he had some successes, but was chiefly remembered for the "Winter of Discontent" in 1978–79. During a very cold winter, his battle with trade unions led to massive strikes that seriously inconvenienced the public, leading to his defeat in the polls by Margaret Thatcher.

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