During the twentieth century, Britain experienced several radical transformations of its sexual-health policies and services. These developments brought huge benefits and helped to break down the stigma and inequalities that impeded access to care. Yet fundamental problems remain. Compounding these problems, sexual-health services are threatened by a looming crisis of antibiotic resistance and funding cuts to Local Authorities. History has much to teach us as we face such challenges. Understanding the historical impact of clinical practices, social conditions, cultural attitudes and policy interventions enables us to recognise long-term trends and patterns. And it makes us better equipped to tackle persistent and emerging challenges in sexual-health outcomes, service delivery and service-user experiences. I am heading an interdisciplinary project that arms us with this knowledge, tracing sexual health in Britain from the end of the First World War to the beginning of the AIDS epidemic. Today, sexual health is defined as the ability to lead a pleasurable and safe sex life and is recognised as a vital component of overall health and wellbeing. Historically, its definition was much narrower. In clinical practice, it meant combating syphilis and gonorrhoea, the principle 'venereal' diseases (VDs) preoccupying health authorities. In the public imagination, it meant remaining morally and eugenically 'fit' to ensure the future health of the race and nation. Gradually, sexual health ballooned, becoming its own clinical field and encompassing a variety of other, newly identified VDs like chlamydia as well as diverse provisions for maternal welfare and family planning. Key to this project is Britain's state-funded VD Service. Established in 1918 and integrated into the NHS after 1948, it was a vital part of Britain's shift towards socialised medicine. Millions of patients passed through its nationwide network of clinics. Yet the entire scheme has been overlooked by all but a handful of scholars. Building on their work, we employ new methods and underused archives to push into understudied time periods, places and themes. We take inspiration from a growing collection of transnational sexual-heath histories, exploring Britain's involvement in initiatives set up by the League of Nations and, later, the WHO to understand how regional politics and culture has influenced responses to global challenges. And because the project prioritises service-user experiences, an important focus is on oral histories that we will conduct with people who accessed or staffed clinics between 1948 and 1980. The project addresses major gaps in the history of sexual health and provides vital context for current problems. But in exploring historical sexual health, it also foregrounds a range of themes in British history. For example, the VD Service was intended to help overcome gender, class and racial inequalities in access to healthcare. Certainly, this government initiative went a long way towards correcting a variety of social injustices and endemic health challenges. But in practice, within the clinics and wider society, prejudices and stigma persisted for decades and continue even into the present. Women and the working classes continued to be viewed as 'vectors' of contagion, in need of management and surveillance. The structural violence faced historically by LGBTQ+ communities within healthcare continues today to undermine their wellbeing and health outcomes. Similarly, institutional racism continues to have a damaging impact on BAME sexual-health experiences. With its robust research, policy and engagement programme, the project will enrich humanities and health research, build public understandings of sexual health, inform policy, augment clinical training and create more reflexive practices among health workers. In so doing, it will have long-term benefits in improved sexual-health outcomes and service-user experiences.