Critical research on digital influence and micro targeting has generally focused on privacy violations by commercial marketers and Cambridge Analytica-style political manipulation. But increasingly, the UK government, police, and security services are using these tools for public policy. The targeted advertising and influence platforms give public sector actors complex tools with which to target behaviour change communications - allowing them to tailor nudge messages based on online behaviour, interests, and fine-detail location. This is allowing the police to use targeted behaviour change advertising to attempt to prevent crime before it happens - but poses serious questions for accountability, ethics, and privacy. Drawing on a dataset of more than 12,000 government adverts from the Meta Ad Library and in-depth interviews with law enforcement, we map the landscape of what we call 'influence policing' in the UK, and discuss the ethical and democratic implications of this new mode of policing.