This paper proposes a new perspective on how radicalisation occurs. It argues that in group-based environments, radicalisation occurs on an ideologically-agnostic omni-directional spectrum of engagement vs disengagement where susceptibility to influence – not a commitment to a particular ideology at the outset – is a precursor to violent extremism. By using behavioural economics as a framework to organise information, particularly through the lens of an availability cascade, we can observe how influence underpins not only radicalisation, but the master narratives and grievances ideologies depend on. While the role of an ideology, or many ideologies, remain an important feature of radicalisation, this paper argues that the ability of an extremist availability entrepreneur to exert influence onto others across a ‘Radicalisation Spectrum’ is a constant a feature among those radicalising. This perspective accounts for an increasingly mixed ideological landscape among non-violent and violent extremists and concludes that a person’s susceptibility to influence is therefore a consistent marker for evaluating a person’s risk of radicalisation.