The activities of the London Journeymen Millwrights Society were the catalyst for the first general Combination Act of 1799. Though a tiny local trades club, its reach throughout the major industries and services of the metropolis at that time made it a target for suppression by major commercial and political forces of those war times – the City of London Corporation and the government of William Pitt. Covering the last decades of the eighteenth and early decades of the nineteenth centuries, the study is set against the background of the technological and economic developments of the early industrial revolution. The disputes between masters and journeymen millwrights over the removal of traditional craft practices and lengthy, time-served apprenticeship laws, led to the emergence of a new breed of capitalist engineering employers in the London area. It involved side-lining the traditional ‘all-round’ time-served millwrights and their replacement by specialist engineers (fitters, filers, turners), in what was called an ‘engineering economy’. By contrast, the legacy of the journeymen millwrights’ trade club is found to be their sophisticated democratic constitution, large parts of which would be adopted by future generations of engineering and other trade unions.