Paul Ayshford Methuen, 4th Baron Methuen, zoologist, painter and landowner, was the eldest child of Field Marshal Paul Sanford Methuen, 3rd Baron Methuen, and his second wife, Mary Ethel, born Sanford. He received his schooling at Eton and then studied zoology and engineering at New College, University of Oxford, where he obtained a BA(Hons) degree in natural science in 1910 and was awarded the MA degree in 1914. In 1908 he visited South Africa on his summer vacation from Oxford and made a collection of freshwater crustaceans in the lakes of the Carolina District of the Transvaal. He described the collection in a paper published in the Proceedings of the Zoological Society of London in 1910.
In 1910 Methuen succeeded John Hewitt* as assistant responsible for invertebrates at the Transvaal Museum (now the Ditsong Museum of Natural History, Pretoria), where he remained until 1914. However, he did not confine his research activities to invertebrates, but also collected batrachians and other amphibians, reptiles, crustaceans and other taxa. In 1911 he visited Madagascar, among others to collect specimens for the University of Oxford Museum, and in 1912 undertook a scientific expedition to German South West Africa (now Namibia). His collection activities led to many papers, several of them in collaboration with Hewitt (who became director of the Albany Museum, Grahamstown, in 1910). A number of these papers were published in the Annals of the Transvaal Museum and dealt with a new Transvaal fish (1911), Transvaal crustaceans (in 2 parts, 1911), collections of reptiles (1913) and batrachians (1913) made during his visit to Madagascar, the zoological specimens collected by the Percy Sladen Memorial Expedition to Great Namaqualand during 1912-1913 (1914), and new species of reptiles and batrachians he collected on the Karasberg in Namibia (1914).
Methuen was a member of the Royal Society of South Africa and, with Hewitt, contributed papers on new South African Batrachia and Lacertilia (1913) and the anatomy of chameleons (1914) to its Transactions. During 1912 and 1913 he also presented four papers at meetings of the Transvaal Biological Society, dealing with his visit to Madagascar and specimens he had collected in the Transvaal. His collection of amphibians from Madagascar went to the Albany Museum, followed by prehistoric stone artefacts he had collected in Namibia (1913). His last scientific paper on specimens from South Africa was published in the Proceedings of the Zoological Society of London in 1919.
During World War I (1914-1918) Methuen was on active service in France as a lieutenant in his father's regiment, the Scots Guards. After the war he obtained a Diploma in Agriculture (1920) and from 1925 worked as a livestock officer at the Ministry of Agriculture, where his experience in slaughterhouses made him a lifelong vegetarian. He succeeded his father as 4th Baron Methuen in 1932.
Methuen had studied drawing at Eton and in Oxford and established a reputation as a serious artist. His preferred subjects were urban views and outdoor scenes with buildings, animals, and plants.
In 1939 he rejoined his regiment and served as staff captain in the London district. Later he was moved to the Procurement and Fine Art Branch, which was established to protect works of art during the invasion of the continent. After the war he recounted his experiences in his book Normandy Diary (1952). His later years were spent mainly in restoration work on his family property, Corsham Court, and in restoring and expanding its art collection. He published a history of the collection in 1958, and a catalogue of the miniatures in 1970.
Methuen was elected an associate of the Royal Academy in 1951. From 1940 to 1967 he was president of the Royal West of England Academy in Bristol. He was a trustee of both the National Gallery (1938-1945) and of the Tate Gallery (1940-1945), a member of the Royal Fine Arts Commission (1952-1959), a trustee of the Imperial War Museum (1950-1952), a Fellow of the Society of Antiquaries, and an honorary Fellow of the Royal Institute of British Architects. He was awarded honorary doctoral degrees by the University of Bristol in 1963 and by the University of Bath in 1970. In 1915 he married Eleanor (Norah) Hennessy, but they had no surviving children.