This article explores the banning of National Action (NA), a small, violent national-socialist group, which, in December 2016, became the first extreme right-wing group proscribed by a British government since 1940. It charts how NA evolved from public order irritant to its designation as a ‘terrorist’ group. Following a short overview of NA’s history and politics, and the circumstances in which the government banned it, the article assesses the ban’s impact upon its activists and milieu. Several subsequent trials have highlighted the ban’s success in dismantling NA as an organization. However, this case study also suggests that it has engendered a period of ideological and organisational adaption as former activists sought out new modes and methods of activism to enable them to circumvent the ban, highlighting the tactical flexibility of extreme right militancy. In line with the wider literature, this case study finds that although the ban succeeded in deterring some activists, others remained defiant, continuing to operate clandestinely until the police disrupted their activities. The article concludes with a discussion of where the ban has been less successful, highlighting the protracted difficulties faced by the authorities in eradicating NA’s digital footprint - one of the aims of banning the group in the first place, since the tools to do so lie with social media conglomerates and are thus largely beyond government control.