How do the depth of-democracy and the style of protest policing affect the level of collective violence? I will measure and test these concepts by applying them to Great Britain in I999- 2009. I will measure the level of collective violence using event analysis and quantitative indicators (violent public order offences, complaints of excessive force used by police officers, financial cost of property damage, and injuries at protest events). My findings show that collective violence generally declined over the period (the middle years were remarkably peaceful), but violence returned in the final year. Adapting Charles Tilly's theory of collective violence, I will suggest this mini-'civilising process' can be explained by both a general trend towards 'harder' policing, which in effect fortified the state monopoly in legitimate violence, and a general trend towards 'deeper' democracy, which reduced the number of protests on the streets. But, like a 'supply-side shock', the financial crisis in 2008 undermined the social democratic trend. I will argue that the long drift towards 'hard' policing and a return to collective action in 2009 led to increased collective violence. The conclusion I draw is that 'deeper' democracy is a more effective dampener of collective violence in the long-run: 'Hard' policing can reduce collective violence, but only so long as the state's own institutions of social incorporation keep it legitimate.