Professor Geoffrey Burnstock, former head of the department of anatomy and embryology (later developmental biology) at University College London (UCL), was a pioneering neuroscientist who developed the concept of purinergic signalling, revolutionising our understanding of how nerves communicate in the body. He was born on 10 May 1929 in London into a working-class Jewish family. His father, James Burnstock, was a clerk whose lungs had been damaged while fighting in the First World War on the Somme; his mother was Nancy Burnstock née Green. He grew up in west London and went to Greenford County Grammar School. He wanted to be a doctor, but failed to get into King’s College, London to study medicine. After doing his National Service in the RAF, he took further courses in science at Kingston College of Technology and then applied again to King’s. Despite being an atheist, he won a place to study theology, was later allowed to add zoology and gained a BSc in 1953. He went on to study for a PhD at King’s and UCL on motility in the guts of fish. In 1956, he moved to the physiology department at the National Institute for Medical Research, Mill Hill, London as a postdoctoral fellow with Wilhelm Feldberg. Here he developed a method for recording the electrical activity and contractions of muscles in the guts of mammals. He moved on to the pharmacology department at Oxford to work with Edith Bülbring, and then, in 1959, relocated to Australia, to the University of Melbourne, where he was a senior lecturer and eventually, in 1964, chair of the zoology department. During the 1960s and early 1970s he worked on smooth muscles – muscles found in the walls of the stomach, intestines, veins and elsewhere, which move involuntary. He established that, even if he prevented all known neurotransmitters from functioning, the muscles continued to be activated – proving that some other, as yet undiscovered, neurotransmitter or neurotransmitters must be at work. After a lengthy process of elimination, he discovered that adenosine triphosphate (ATP), usually associated with the production of energy within the cell, was the neurotransmitter activating the smooth muscle and Burnstock coined the term ‘purinergic signalling’ to denote its function. This work proved that Dale’s principle, established by Nobel prize winners Sir John Eccles and Sir Henry Dale, that individual nerve cells do not release more than one neurotransmitter, was false. His work was initially ridiculed, but by the early 1990s and the discovery of ATP receptors within muscles and nerves, his ideas became more widely accepted. The concept of purinergic signalling led to the development of new drugs, including clopidogrel, which helps prevent strokes and deep vein thrombosis, and potential new treatments for cystic fibrosis and cancer, among other conditions. In 1975 Burnstock returned to England as head of the anatomy and embryology department at UCL. Here he led a large and vibrant research group, with many overseas visitors. He retired from his departmental role at UCL in 1997, but continued his research, moving to the Royal Free Hospital School of Medicine, where he ran the Autonomic Neuroscience Institute until 2004, afterwards serving as its president. In 2017 he finally retired at the age of 88 and he and his wife moved back to Melbourne, where he was an honorary professor at Melbourne University. He was the first president of the International Society for Autonomic Neuroscience and editor-in-chief of the *Purinergic Signalling* journal. He was elected a fellow of the Royal Society in 1986 and received the Society’s gold medal in 2000. In 2017 he was awarded the Australian Academy of Science’s Macfarlane Burnet medal. In 2018 he was appointed as a Companion of the Order of Australia. Burnstock died in Melbourne on 2 June 2020 at the age of 91. He was survived by his widow Nomi (née Hirschfield), a PhD student in cell biology from New Zealand he had married in 1957, their daughters Aviva, professor of conservation at the Courtauld Institute of Art, Tammy, a director, producer and screenwriter, and Dina, an artist, and seven grandchildren.