William Joscelyn Arkell was born at Highworth, Wiltshire on 9 June 1904, the seventh and youngest child of James Arkell, a partner in the local brewery, and his wife Laura. “A deeply rooted love for the English countryside influenced Arkell from an early age. Alone or with a brother he explored every land, spinney, hedge and ditch around Highworth, collecting insects, snails, plants and fossils … The family summer holidays, always spent at Swanage, afforded opportunities for the Dorset coast and interior to be explored with equal thoroughness, on foot or by bicycle”. 
After a boarding-school education, Arkell entered New College, Oxford, in 1922. By this time he had decided to make geology his career and to relegate entomology, his other great passion, to second place among his interests. This decision was reinforced by the inspiration and encouragement of W.J. Sollas, a versatile, enthusiastic man who was then Professor of Geology. In 1925 he gained the only first-class honours in geology in his year, and a year later he was awarded the Burdett-Coutts Scholarship for work on the Corallian rocks of the Oxford district. Very soon he was writing his first papers, and by 1927 he was ready to take his D.Phil., a degree then only recently introduced.