Arthur Wallis Exell at his cottage in Blockley (1991)

Arthur Wallis Exell OBE (21 May 1901 in Birmingham – 15 January 1993 in Cheltenham)[1] was initially an assistant and later Deputy Keeper of Botany at the British Museum during the years 1924–1939 and 1950–1962.[2] A noted cryptographer, taxonomist and phytogeographer, he was notable for his furthering of botanical exploration in tropical and sub-tropical Africa, and was an authority on the family Combretaceae.[3]
Exell’s formal education started at Queen Elizabeth Grammar School in Warwickshire, and then King Edmund’s School in Birmingham. From there he went on to Emmanuel College, Cambridge[4] and was awarded an M.A. in 1926,[5] having joined the British Museum as a second-class assistant on 11 August 1924, eventually becoming Deputy Keeper of Botany in 1950. He was entrusted with the Polypetalae, although his first paper was a morphological study of the hymenium in three species of fungus.
Exell’s first contact with Africa was in 1932/3 when he travelled to the islands in the Gulf of Guinea – São Tomé and Principe, Bioko and Annobon.[6] His reports on the expedition were published in 1944 as a “Catalogue of the Vascular Plants of S. Tome”, which for many years served as the standard reference to the islands’ flora. The expedition also acquainted Exell with the Portuguese botanists Luis Carrisso and Francisco de Ascensão Mendonça of Coimbra University. Accompanied by them and his wife, Exell launched into a study of the flora of Angola, at that time a Portuguese colony. Also in their group was John Gossweiler (1873–1952), the government botanist in Angola. During the journey Carrisso suffered a fatal heart attack.[7] Exell continued his collaboration with Coimbra University and Mendonça, publishing the first volume of the “Conspectus Florae Angolensis” (1937–1951).[8]
During the Second World War, Exell’s knowledge of Portuguese – he was also fluent in French and German – led to his being seconded to the Government Communications Headquarters at Bletchley Park, and working as a cryptographer in Cheltenham.[9] Returning to the British Museum (Natural History) in 1950, he founded the ‘Association pour l’Etude Taxonomique de la Flore d’Afrique Tropicale’ (AETFAT) and started the Flora Zambesiaca project, the flora covering the catchment area of the Zambesi River, which at the time comprised the Federation of Rhodesia and Nyasaland, Bechuanaland, the Caprivi strip and Mozambique