The crowd can be both euphoric and menacing at once, and it's a phenomenon that urban scholars identify as a form of informal urbanism: shaping cities through self-organisation, oscillating inside and out of formal urban regulation. Kim Dovey, director of the University of Melbourne's Informal Urbanism Research Hub, InfUr-, joins Jonathan to talk about the paradoxes of informal urbanism, and what makes the 'good' or 'bad' crowd.