Labour-only subcontracting, or lump labour, was a type of employment system whereby a contractor would hire, on a labour-only basis, a subcontractor, which was often an individual worker or a collection of individuals, and pay a lump sum for an agreed amount of work. It was a form of self-employment which was not new in the construction industry, but which rose exponentially in the post-war decades, particularly in London and the South of England. The attractions of labour-only subcontracting were obvious from the viewpoint of the major contractors. Because the labour-only workers were legally self-employed, the major contractors paid no national insurance contributions, sick pay, or holiday pay etc. This meant they were able to pay workers a higher rate of pay, which in turn allowed them to continually recruit the skilled labour that was sometimes in short supply. Agreements between contractors and labour-only workers were individual contracts, which were negotiated outside of the collective bargaining structures of the industry. The ‘lump’ workers, therefore, had no vested interest in collective action or collective struggle. Concerns over health and safety, the length of the working day, and wage rates, all of which exercised the attention of the trade unions in this period, meant little to lump workers, whose only concern was to finish the job quickly and move on. As a result, the rise of labour-only subcontracting was matched by a steep decline in trade union membership in the industry. Some building workers were forced by the major contractors to go on the ‘lump’ as the only way of getting work. Trade union activists regarded labour-only subcontracting as a malicious system that would destroy site organisation and eradicate hard-fought rights and conditions and tried to fight back. As a result, in the period that our research examined, there were many disputes on construction sites that centred on the issue of labour-only subcontracting. It is a system that continues to pose a huge challenge to construction trade unionism in Britain today.