While Raven's principal professional occupation was his career as a classical scholar, he applied a similar intellectual rigour to his amateur interest in botany.
From the mid-1930s John Heslop-Harrison, Professor of Botany at King's College, Newcastle upon Tyne, had reported significant new plant discoveries on expeditions to the Inner and Outer Hebrides. The sheer scale of the discoveries aroused scepticism, and in 1948 Raven secured a grant from Trinity College to fund a trip to Harris and Rùm in July and August of that year to investigate the claims of Heslop-Harrison. Raven's conclusions about two of the notable species were published, briefly, in Nature. He suggested that both Carex bicolor and Polycarpon tetraphyllum were introductions to Rùm, but did not comment on the possible means of introduction. His full report of the expedition and fraud was deposited in the library of King's College, Cambridge on 5 May 1960, to attack Prof. Jack Heslop-Harrison's electron microscope research into plant genetics and only published in full in 1999 after the deaths of both Heslop-Harrison, his son Jack Heslop-Harrison and Raven himself. In the report Raven alleged that at some time in the 1940s Heslop Harrison transported alien plants to the Isle of Rum and planted them in the soil; he then "discovered" the plants, claimed they were indigenous to the area and that he was the first to find them. Raven's report to the council of Trinity College states: "In the interests not only of truth but also of the reputation of British science it is essential somehow to discover what plants and what insects he has either completely fabricated or else deliberately introduced into the Hebrides." Raven's classical and botanical interests were brought together in four J. H. Gray Lectures given at Cambridge in 1976, published after his death as Plants and Plant Lore in Ancient Greece.
Family
Raven married Constance Faith Alethea Hugh Smith; they had five children: Anna Raven, Andrew Raven, Hugh Raven, Sarah Raven and Jane Raven. On marriage in 1954 John and Faith Raven purchased Docwra's Manor in Shepreth, near Cambridge, where they cultivated a garden which is now open to the public. He died on 5 March 1980 in Shepreth, near Cambridge, aged 65. Following his death a group of friends contributed to a collection of essays to commemorate his life, published in 1981 as John Raven by his Friends.
Selected publications
Pythagoreans and Eleatics: An account of the interaction between the two opposed schools during the fifth and early fourth centuries B.C, Cambridge University Press, 1948
Mountain Flowers, Collins 1956
Presocratic Philosophers: A Critical History with a Selection of Texts, Cambridge University Press, 1957
Plato's Thought in the Making: a Study of the Development of His Metaphysics, Cambridge University Press 1965