Leonard James Callaghan, Baron Callaghan of Cardiff, KG, PC , was Prime Minister of the United Kingdom from 1976 to 1979. Known as Jim for short , Callaghan is the only person to have served in all four of the Great Offices of State: Prime Minister, Chancellor of the Exchequer, Home Secretary and Foreign Secretary.

Callaghan was Chancellor of the Exchequer from 1964 to 1967 during a turbulent period in the British economy in which he had to wrestle with a balance of payments deficit and speculative attacks on the pound sterling. In November 1967, the Government was forced to devalue the pound sterling despite having denied he would do this publicly including to the House of Commons. Callaghan offered to resign, but was persuaded to swap his ministerial post with Roy Jenkins, becoming Home Secretary from 1967 to 1970. In that capacity, Callaghan took the decision to deploy the British Army in Northern Ireland, after a request from the Northern Ireland Government.