Analysis of UK employment and labour law is often characterised by a curious dissonance. The overarching narrative mandates that labour law is a countervailing force to the inequality of bargaining power, embedded with values and assumptions concerning the nature of employment relations and the role of labour law. [---] This paper seeks to bridge that gap, by offering a legal realist account of the legal doctrine that governs the employment of agency workers, focusing on the ‘necessity’ and ‘sham’ tests. It assesses the legitimacy of importing legal tests from one (commercial) context to another (employment) context; questions the courts’ protestations that their use is mandated by precedent; and outlines the real implications for the status and rights of agency workers in the UK.