On May 29, 1969, London’s newspapers carried dramatic headlines: “Donor’s Heart ‘Switched Off’ by Doctors.” Margaret Sinsbury had died in Guy’s Hospital, after which her heart was removed and transplanted. This, the third British heart transplant, crystallized the deep concerns that were by then swirling around the wider transplant enterprise, notably whether the people from whom organs were being taken were dead or had been made so. Yet a year earlier, to reassure the public in this regard, a formula had been devised at the U.K. Health Ministries’ MacLennan Conference to enable death to be certified based on cerebral rather than cardiac indicators. This was the first such formula in the English-speaking world, and it included safeguards to protect the interests of dying patients who were considered to be potential organ donors. However, the third British heart transplant revealed these protections to be a chimera, and brought such operations there to a halt for a decade.