break the mould put an end to a pattern of events or behaviour, especially one that has become rigid and restrictive, by doing things in a markedly different way.

☞ Originally this phrase referred to casting artefacts in moulds: destroying a mould ensured that no further identical examples could be produced. The expression became a catchphrase in Britain in the early 1980s with the foundation of the Social Democratic Party. Its founders promoted the party as breaking the 'out-of-date mould' of British politics, a phrase used by Roy Jenkins in a speech in 1980.