(1910-1977), neurophysiologist William Grey Walter (also known as Grey Walter) was born in Kansas City, Missouri, on 19 February 1910 to journalist parents Karl Wilhelm Walter (1880-1965) and Minerva (Margaret) Lucrezia Hardy (1879-1953). The Walter family moved from the United States to Britain in 1915, where William remained for the rest of his life. He was educated at Westminster School (1922-1928), before taking the Natural Science Tripos at King’s College, Cambridge (1928-1931). He went on to pursue postgraduate research on nerve physiology and conditioned reflexes, gaining his MA in 1935. After completing his MA, Walter was invited to work at the Central Pathological Laboratory of the Maudsley Hospital, London, under neuropsychiatrist Frederick Lucien Golla (1877-1968). Since the late 1920s, Golla had become increasingly interested in the clinical applications of the burgeoning field of electroencephalography (EEG), the measurement of the electrical activity of the brain via electrodes placed on the scalp. Noting his skill in technical matters, Golla encouraged Walter to develop increasingly sophisticated EEG devices, and supported his application for a Rockefeller Travelling Fellowship to visit the Jena laboratory of German physiologist Hans Berger (1873-1941), widely credited as the founder of electroencephalography. Walter went on to achieve several key ‘firsts’ in electroencephalography, including the first detection of a cerebral tumour using the technique in 1936. Between 1936 and 1939, Walter expanded his research programme and took readings from hundreds of patients, focusing particularly on the electrical patterns of epilepsy. In 1939, Golla was invited to become director of the new Burden Neurological Institute, Bristol, an independent research unit specialising in the investigation and treatment of neurological, psychological, and psychiatric disorders, and invited Walter to become director of the Institute’s Physiology Department. At the Burden, Walter further developed his EEG apparatus, developing the automatic frequency analyser and the toposcope in 1943 and 1950 respectively. His research programme also became increasingly ambitious, with investigations into the cerebral effects of stroboscopic light beginning in 1947 and, later, the discovery of ‘contingent negative variation’ (CNV, or the ‘expectancy wave’) in the 1960s. Walter also played a key role in the professionalization of electroencephalography during this period, co-founding the journal Electroencephalography and Clinical Neurophysiology and organising meetings of the EEG Society (1943-1989). Outside of his clinical work, Walter became a key figure in early British cybernetics, the study of feedback, control, and communication systems in humans and machines that synthesised approaches from engineering, biology, and mathematics. He co-founded the Ratio Club, an informal dining and discussion group which provided a key social outlet for cybernetic enthusiasts, which met between 1949 and 1955. He also built several cybernetic devices in his spare time, the most famous of which were his robotic tortoises, or Machina Speculatrix, designed to function as simple models of the adaptable human brain. These received national attention when they were exhibited on television in 1950 and at the Festival of Britain in 1951. He also became a prolific public intellectual, writing 170 scientific publications, serving as an expert witness in court courses, appearing frequently on the BBC, and writing an immensely popular non-specialist text on his neuroscientific work, The Living Brain (1953). His work also gained a surprising popularity among counter-cultural artists during the 1950s and 1960s, including Beat writers William S. Burroughs and Allen Ginsberg, who saw Walter’s research as part of a broader investigation of human consciousness. Walter was married twice, first to Katharine Monica Ratcliffe in 1934 and then to Vivian Joan Dovey (1915-1980) in 1947, with whom he had one son, Timothy Walter (1949-1976). Walter and Dovey separated in 1960 and divorced in 1973. After their separation, Walter lived with Lorraine Josephine Aldridge (née Donn) until 1972. In 1970, Walter suffered severe brain damage following a road accident, forcing him to retire from full-time research work. He died of a heart attack in 1977.