BACKGROUND: Bristol City Council introduced a new advertisement policy in 2021/2022 which included prohibiting the advertising of unhealthy food and drink (HFSS), alcohol, gambling and payday loans across council-owned advertising spaces. This mixed methods study is part of the BEAR study, and aimed to explore the rationale and the barriers and facilitators to implementing the policy, and describe the perceived advertising environment prior to implementation. METHODS: Semi-structured interviews were carried out with seven stakeholders involved in the design and implementation of the advertising policy. A stakeholder topic guide was developed before interviews took place to help standardise the lines of inquiry between interviewees. A resident survey was developed to collect socio-demographic data and, for the purpose of this study, information regarding observations of advertising for HFSS products, alcohol and gambling. RESULTS: Fifty-eight percent of respondents residing in Bristol and South Gloucestershire reported seeing advertisements for unhealthy commodities in the week prior to completing the survey. This was highest for HFSS products (40%). 16% of residents reported seeing HFSS product advertisements specifically appealing to children. For HFSS products in particular, younger people were more likely to report seeing adverts than older people, as were those who were from more deprived areas. An advertisement policy that restricts the advertisement of such unhealthy commodities, and in particular for HFSS products, has the potential to reduce health inequalities. This rationale directly influenced the development of the advertisement policy in Bristol. Implementation of the policy benefitted from an existing supportive environment following the 'health in all policies' initiative and a focus on reducing health inequalities across the city. CONCLUSIONS: Unhealthy product advertisements, particularly for unhealthy food and drinks, were observed more by younger people and those living in more deprived areas. Policies that specifically restrict such advertisements, therefore, have the potential to reduce health inequalities, as was the hope when this policy was developed. Future evaluation of the policy will provide evidence of any public health impact.