Leonard Colebrook was born in Guildford on 2nd March 1883 and received his education at Guildford Grammar School, the High School, Eastbourne, and Christ’s College, Blackheath. He studied medicine at St Mary’s Hospital, London, graduating MB, BS in 1906. As a student he had been greatly influenced by Almroth Wright and after qualification joined his team at St Mary’s as a research bacteriologist. An early interest was wound infection, especially by streptococci, and during the first World War he continued this work in France, in particular looking for a treatment that would attack the infecting organism without damaging the human body. After the war he was appointed to the staff of the Medical Research Council and returned to St Mary’s where he became involved in the classification of haemolytic streptococci. When the Interdepartmental Committee on Maternal Mortality was set up by the Minister of Health in 1928, Colebrook was invited to serve on it as the bacteriologist (fig 1). In 1930 he was seconded to become Director of the Bernard Baron Research Institution at Queen Charlotte’s Hospital in London where an isolation block, under the direction of the resident medical officer, Dr Maeve Kenny, had been opened to take cases of puerperal fever from the whole London area.1^–3 Over the next few years he and his team studied the causes and prevention of puerperal sepsis, culminating in 1936–37 in the successful treatment of this condition using first prontosil and then the sulphonamides. Colebrook later described these exciting developments in a review article in 1956.4 First though it should be mentioned that in the 1920s Rebecca Lancefield and others had been able to classify haemolytic streptococci strains into a number of sub-groups including the Group A responsible for most …