This report aims to aid understanding of how multi-agency partners, including police and justice, health and social care, local government, education, and the third sector, can work together to prevent harms that cross the public health and criminal justice landscape, such as violence, substance use and mental health. It provides examples of ways in which multi-agency partners can work to implement whole system approaches to addressing harm and examines areas where early intervention and preventative policing approaches have been or are likely to be successful.