Since the mid-2010s, public health has increasingly been recognised in the UK as one of many gambling harms affecting individuals and society at a time when public health teams had just moved into local government. There is no legal requirement for local public health teams to be involved in decisions on licencing gambling premises, and several gambling activities (such as the National Lottery and online gambling) fall outside of local government’s direct influence. Consequently, these teams must find innovative ways to tackle these growing threats to health. My research aimed to identify levers and barriers that local authorities in London can adopt to address health-related gambling harms. It used a mixed method approach to identify the underlying “mechanisms” that can support or hinder this approach. I found an increasing concentration of gambling outlets in deprived areas but also a dominant discourse that conceptualises gambling as a “fun” leisure activity and legislation that seek to confine local government within the narrow silo of land-based licensing. Surveys and interviews with local public health teams revealed a broad range of interests and influences on gambling policy, but effective action was hindered by their lack of power, financial resources, and knowledge of effective interventions. A poor evidence base exacerbated the situation, much industry-funded and thus downplaying effective measures. The underlying mechanisms identified in the mixed methods analysis were a tolerance of harm by society, influence exerted by the gambling industry, disempowerment of local government, and heterogeneity (of local government, of public health teams, and of gambling products). These mechanisms can counteract, moderate, or reinforce each other and whether they lead to action is highly context-dependent. I have used these findings to create a list of recommendations for local public health teams.