 His retirement as Regius Professor of Surgery at the University of Glasgow was announced in December 1963 in the London Gazette by the Scottish Home and Health Department, along with the news of his appointed successor Andrew Watt Kay, though the retirement did not take effect until the following year on 30 September 1964.As well as practising, teaching and administrating as Glasgow's Regius Professor of Surgery, Illingworth also held positions within the hierarchies of a range of medical and learned societies, colleges and associations.In 1955 he was President of the Association of Surgeons of Great Britain and Ireland, and President for two terms of the Society of Academic and Research Surgery (1956 and 1957).