Born at Southampton in 1889, the son of Henry Osborn. In 1914 he was the first medical missionary appointed by the WMMS to serve in Southern Rhodesia. The hospital at Kwenda was an isolated and unhealthy location in Mashonaland and he was forced to return home in 1918 on health grounds. He died in 1961.
His nephew, Sidney B. Osborn (1918-2011), named after him, was born in Leeds in 1918 and educated at Highgate School after the family had moved to London. In 1937 on health grounds he had to give up his plans to follow his uncle as a medical missionary and took up a career as a medical physicist, first at the Middlesex Hospital and from 1943 at University Hospital, London. In 1962 he obtained his PhD and was appointed Director of Medical Physics at King's College Hospital, where he did pioneering work on radiation safety, including the early use of radioisotopes. An 'occasional' consultant to the World Health Organisation, he travelled widely and offered his help to Methodist hospitals whenever he found himself in their vicinity.
Retiring in 1978 he served as honorary treasurer of the Division of Ministries until 1992, employing pastoral and practical as well as financial skills. He and his wife sang in the choir at Ballard's Lane Methodist church, Finchley and belonged to the Methodist Church Music Society. His other enthusiasms included genealogy and philately.