He was 18 months old when his parents left Cornwall and emigrated with him to South Africa, where his father worked as a miner. Humphry had a disrupted school life. In 1944 he joined the South African Naval Forces and was seconded to the Royal Navy, in which he served as an able seaman and fought in the seas of the Far East. After the Second World War he returned to South Africa and entered Witwatersrand University, initially to study medicine, then changing to zoology. His passion for the sea and fishes was shaped by childhood fishing expeditions, his time in the Navy and, further, by the discovery in 1938 of the "living fossil" coelacanth fish off East London.
Having graduated he became a Colonial Office Fisheries Research Student based at the East African Fisheries Research Organisation at Jinja, Uganda, on the shore of Lake Victoria, and in 1951 was appointed its Research Officer. Greenwood discovered that the many perch-like cichlid fishes which populated the lake represented scores of undescribed species. Although superficially alike they differed markedly in their diets, feeding and breeding behaviours. He realised that Lake Victoria represented a laboratory of evolution akin to an oceanic island but of greater magnitude in terms of numbers of species and speed of evolutionary change.
With his first publication, in Nature in 1951, putting this aspect of the African Great Lakes on the evolutionary map, began 40 years of systematic studies of Lake Victoria cichlids. His work took him to the Natural History Museum in London to consult with the then cichlid expert, Ethelwynn Trewavas. In 1958 he was appointed as Senior Research Fellow there and in 1959 taken on the permanent staff as a Principal Scientific Officer.
Greenwood's interests broadened to embrace the comparative anatomy and classification of fishes generally and the parallel interests of colleagues in the United States resulted in 1966 in a collaborative benchmark paper on the classification of bony fishes. The advent in the early Seventies of cladism, whereby evolutionary relationships were seen as dichotomous branching patterns based on shared specialisations, was accepted by Greenwood and eagerly applied to the Lake Victoria cichlids.
Greenwood was no stick-in-the-mud, hidebound by preconceived theories. The museum's Fish Section became a Mecca for the world's ichthyologists. Greenwood had a great sense of humour and was a raconteur whose often colourful language delighted rather than offended. He was meticulous in his descriptive and anatomical work and never happier than when studying complex anatomical situations; although not a true functional morphologist he had a "holistic eye" and was readily able to appreciate the functioning of particular systems within larger ones. He was equally meticulous in his correspondence, on which he would spend an inordinate time; no detail would be spared.
From 1967 to 1974 Greenwood was chairman of the International Biological Programme subcommittee on Lake George, a total investigation of that Ugandan lake's limnology and biology. The investigating team's work was overseen from London by Greenwood supplemented by field visits. It was an arduous task generating considerable correspondence and frequent meetings.
Having served as Zoological Secretary of the Linnean Society of London, Greenwood was elected as President in 1976 and this and other committee work eroded his research time. His usual comment to me after a meeting was, "That was a complete bloody waste of time, now let's get on with some real work." He enjoyed his field visits, which gave him to opportunity to see his favourite fish in their natural habitats.
Greenwood supervised several PhD students but, like visitors, they were regarded as something of a mixed blessing. He demanded from them the highest standards and considered they should have come to him already well versed in their discipline. Their manuscripts were read with sharp but always valid criticism and his honing of syntax and grammar was legendary. Although a self- admitted lousy draughtsman, he had an acute artistic eye and was a shrewd and discerning critic of visual art. He had a passion for collecting prints.
Greenwood was elected a Fellow of the Royal Society in 1985 and under the auspices of the society visited China in 1987. The contacts he made there resulted in Chinese zoologists studying in the UK.
Humphry Greenwood had a complex personality; he was authoritative, sometimes unapproachable and evasive, yet also extrovert, humorous and charming. He had a rapid grasp of ideas, problems and situations and the consequences that could arise from them. He was tenacious in the extreme. The Natural History Museum was his real "home" and even after he retired and settled in Grahamstown, South Africa, he visited London on a regular basis.
Although he was never himself an administrator in the museum, his opinions were valued by all levels of staff. He particularly enjoyed the opportunities the museum offered for interaction with the public. He delivered public lectures with aplomb, never referring to notes and immediately capturing the interest of even the youngest members of his audience. He rarely delegated and thoroughly enjoyed getting his hands dirty; he once answered a public enquiry as to the identity of the fishes atop the museum weather-vanes by scaling a precarious sloped roof to investigate them. He believed that scientific work should be presented to the public without frills and deplored what he considered to be a general decline in exhibition standards.
Greenwood was a mine of ichthyological information and it is regrettable that his only general work on the subject is a reworking of J.R. Norman's 1930s A History of Fishes; the magnum opus of his retirement years was not to be. His contributions to his science were many and his influence on his colleagues and students profound; the work he began on Lake Victoria's fishes continues and his obsession with those remarkable creatures will captivate and occupy the lifetimes of his successors.
Peter Humphry Greenwood, ichthyologist: born Redruth, Cornwall 21 April 1927; Senior Research Fellow, Natural History Museum 1958-59, Senior/Principal Scientific Officer and Curator of Fishes 1959-67, Senior Principal Scientific Officer 1967-85, Deputy Chief Scientific Officer 1985-89; FRS 1985; married 1950 Marjorie George (four daughters); died London 3 March 1995.