Since the Second World War, Great Britain has witnessed a recurring escalation and de-escalation of confrontations between extreme right-wing or anti-minority protest groups on the one hand and, on the other, militant anti-fascist or anti-racist groups, and latterly also a number of extreme Islamist groups. In this article, we trace the outline of four waves of these movement–countermovement contests in order to engage critically with ideas of what some academics have called “cumulative extremism (CE)”. Contrary to the tenor of much of the public, policy and academic debate around such contests, we draw attention to what we describe as the missing spirals of violence. In order to better explain and accommodate these empirical findings, we argue that it is important to resist the temptation to reduce “CE” to a process of “tit-for-tat” violence. We outline four factors that have been particularly important in shaping patterns of interactive escalation, de-escalation and non-escalation in the case studies described: the broader strategic aims of activist groups; dynamics of intra-movement control and leadership; the actions of and activist's interactions with state actors; and emergent movement cultures and identities.