ABSTRACT This article presents the first archival case study of the drivers of UK climate policy and the creation of the UNFCCC. I contribute to the literature on the green state and green capitalism, firstly by arguing that existing approaches do not fully capture the state’s and most importantly policymakers’ position in capitalism. Secondly, there remains scope for more refined empirical examination of policymakers and how they navigate the contradictions of environmental policy. I address these weaknesses by analysing newly declassified British governmental documents through form-analytic Marxism, demonstrating the drivers behind the Thatcher government’s climate policies and push for an international convention. I argue that policymakers occupy the site of the state’s contradictory pressures, and thus find themselves ‘beneath the insuperable barrier’ as their commitment to accumulation and capitalist logics supersedes their drive to design ambitious environmental measures. This reveals fundamental tensions with policymakers’ ability to address the climate crisis.