Framed by ongoing debates about both the legitimacy and efficacy of the UK government's Prevent counter-terrorism strategy, this article examines how and why it is resisted and contested in both overt and more nuanced ways. The analysis focuses specifically upon how such contests are manifested in the aftermath of terror events illuminated by two distinct data sources. These are empirical data collected from interviews with policy developers and deliverers, together with material derived from systematic monitoring and assessment of social media following four terror attacks in the UK in 2017. It is suggested that such incidents are singularly important moments because they simultaneously evidence the need for Prevent-type interventions, but...