Basil Morson was a consultant pathologist at St Mark’s Hospital, London and a pioneer of gastrointestinal pathology. He was born in Hampstead, London, one of three sons. His father, Albert Clifford Morson, was a urologist; his mother was Adela Frances Maud Morson née Phene. Through his father, he was related to the 19th century chemist Thomas Newborn Robert Morson, who co-founded the Pharmaceutical Society and pioneered the manufacture of drugs, particularly the opium group. Basil Morton was educated at Beaumont College, Berkshire and Wadham College, Oxford. He then served in the Royal Naval Volunteer Reserve as a sub lieutenant from 1943 to 1946, where he studied diving physiology. Following his demobilisation, he qualified in 1949 from the Middlesex Hospital Medical School with the conjoint examination. He held house surgeon posts at the Middlesex and the Central Middlesex hospitals, and subsequently became an assistant pathologist at the Bland-Sutton Institute of Pathology at the Middlesex Hospital. From 1952 to 1956 he was a morbid histologist at Mount Vernon Hospital, Northwood. He was then appointed as a consultant pathologist at St Mark’s and later became director of the research department there. He was also a senior lecturer in pathology at the Postgraduate Medical School of London, Hammersmith. From 1976, he was a consultant in pathology in the Royal Navy. He retired in 1986. In the 1960s, with Sir Hugh Lockhart-Mummery, he described the special features of colonic Crohn’s disease, and in 1967 demonstrated the histological appearances of dysplasia in ulcerative colitis. He also made significant contributions to the understanding of the adenoma carcinoma sequence. Following the introduction of endoscopy, he pioneered the pathological interpretation of endoscopic biopsies. With Ian Dawson, he wrote the influential first textbook on *Gastrointestinal pathology* (Oxford, Blackwell Scientific Publications, first edition 1972), popularly known as ‘Morson and Dawson’. He was president of the proctology section of the Royal Society of Medicine (from 1973 to 1974) and of the British Society of Gastroenterology (from 1979 to 1980), and treasurer and vice president of the Royal College of Pathologists. Outside medicine, he enjoyed gardening, ornithology, skiing and tennis. In 1950 he married Pamela Elizabeth Gilbert. They had a son, Christopher, two daughters, Caroline and Clare, and a grandson, Sevrin. They divorced in 1982 and he married Sylvia Dutton. He was predeceased by both wives.