Risk-based policymaking is a form of reflexive policymaking that uses risk analysis to address both the primary objects of policy interventions and their secondary adverse consequences. As such, it has become central to debates about efficiency, control and accountability in UK government. To better understand the factors shaping its emergence, this article studies the UK Department for Environment, Food and Rural Affairs’ (Defra) adoption of risk-based policymaking. In-depth interviews with Defra staff suggest that risk-based policymaking serves conflicting objectives and struggles to perform its ostensive functions. The article concludes, first, that risk understandings can be organizationally filtered in ways that reinforce rather than challenge entrenched policy practices. Second, that using risk-based policymaking for audit purposes can undermine policymaking reflexivity. Third, that the value of risk ideas in reconciling competing accountability and blame- avoidance pressures leads to risk ‘colonizing’ increasing dimensions of policymaking.