IntroductionThe Independent Review of the Mental Health Act (MHA) in England and Wales confirmed increasing levels of compulsory detentions, especially for racialised communities. This research aims to: (a) understand the causes of and propose preventive opportunities to reduce the disproportionate use of the MHA, (b) use an adapted form of experience-based codesign (EBCD) to facilitate system-wide changes and (c) foreground the voices of service users at risk of detention to radically reform policy and implement new legislation to ensure the principles of equity are retained.Methods and analysisThis is a qualitative study, using a comparative case study design. This study is composed of five work packages; photovoice workshops will be conducted in eight local systems with service users and healthcare professionals separately (WP1); a series of three EBCD workshops in each local system to develop approaches that reduce detentions and improve the experience of people from racialised communities. This will inform a comparative analysis and national knowledge exchange workshop (WP2); an evaluation led by the patient and public involvement group to better understand what it is like for people to participate in photovoice, codesign and participatory research (WP3); an economic evaluation (WP4) and dissemination strategy (WP5). The impact of the involvement of patients and public will be independently evaluated.Ethics and disseminationThis study is sponsored by the University of Oxford and granted ethical approval from the NHS Research Ethics Committee and Health Research Authority (21/SC/0204). The outputs from this study will be shared through several local and national channels.