This piece of research aims to evaluate the implementation of the new legislation requiring all schools in England to provide Relationships and Sex Education (RSE) from September 2020. As part of the project, we consulted with young people aged 14-25 years old and stakeholders from schools, local authorities, the health sector and agencies supporting sex education in workshops between August-October 2019. The purpose of the workshops was to capture, via system mapping, the stakeholder perspectives on how the new law on statutory RSE may induce change in the system to better inform the evaluation of the implementation of the new legislation. This allowed us to represent the complexity of all the anticipated changes on an overarching system map which can substitute for a logic map and will inform the process and outcome evaluation of the new legislation.