This talk explores the biography of one of Britain’s foremost animal welfare campaigners and the world of activism, science, and politics she inhabited. In 1964, Ruth Harrison’s bestseller Animal Machines triggered a gear change in modern animal protection by popularising the term ‘factory farming’ alongside a new way of thinking about animal welfare. My presentation explores Harrison’s avant-garde upbringing, Quakerism, and how animal welfare debates were linked to concerns about the wider ethical and environmental trajectories of post-war Britain. Breaking the myth of Harrison as a one-hit wonder, it reconstructs Harrison’s 46 years of campaigning and the rapid transformation of welfare politics and science during this time. Exacerbated by Harrison’s own actions, the decades after 1964 saw a polarisation of animal politics, a professionalisation of British activism, and the rise of a new animal welfare science. Harrison’s belief in incremental reform allowed her to form ties to leading scientists but alienated her from more radical campaigners. Many of her 1964 demands gradually became part of mainstream politics. However, farm animal welfare’s marketisation has also led to a relative divorce from the wider agenda of social improvement that Harrison once bore witness to.