In 2015 the UK became the first country in the world to legalise mitochondrial donation, a controversial germ line reproductive technology to prevent the transmission of mitochondrial disease. Dimond and Stephens track the intense period of scientific and ethical review, public consultation and parliamentary debates preceeding the decision. They draw on stakeholder accounts and public documents to explore how patients, professionals, institutions and publics mobilised within ¿for¿ and ¿against¿ clusters, engaging in extensive promissory, emotional, bureaucratic, ethical, embodied and clinical labour to justify competing visions of an ethical future. They describe how this decision is the latest iteration of a UK sociotechnical imaginary in which the