It was disregarded in 1932 over tariff reform when the National Liberals were allowed to remain in the cabinet even though they opposed the Government’s move to protectionism. Harold Wilson suspended it in 1975 by allowing ministers to campaign on either side of the referendum on the common market, as did Jim Callaghan in 1977 over direct elections for the European Parliament. These are apparently used as precedents for the current break down in the principle. However, none really does so.