Radicalisation is the term proposed to explain how an apparently ordinary person can be transformed from a law-abiding citizen into a supporter of violent protest. It refers to a process of belief modification and requires a progression from feeling sympathy towards violence for a political goal to direct involvement in such activities. This paper explores the reasons why individuals are drawn to extreme movements and how approaches devised for public health can be applied to prevention. We argue for interventions at an early stage when ideas are beginning to take root in people vulnerable to the recruiter’s message and identify both protective and risk factors.