William Mallam Espin, surveyor and attorney, was the son of Rev. John Espin* and his wife Catherine Mallam. He was educated at St Andrew's College, Grahamstown, and St John's College, Oxford. He passed the matriculation examination of the University of the Cape of Good Hope in 1887 and in 1892 passed the university's examination for the Certificate of Proficiency in the Theory of Land Surveying. He was admitted as a land surveyor in the Cape Colony in 1895. From 1894 to 1909 he was a partner with Patrick Fletcher* and Robert A. Fletcher* in the firm Fletcher & Espin, which laid out Bulawayo and other townships in Rhodesia (now Zimbabwe). He and Robert Fletcher compiled three maps of Matabeleland. The first, Fletcher and Espin's map of Matabeleland (8 miles to the inch, or 1:506 880) appeared in 1896. The second, Fletcher and Espin's land map of Matabeleland (5 miles to the inch, or 1:316 800) appeared in 1897 and contained their third map, Fletcher and Espin's geological sketch map of Matabeleland (20 miles to the inch, or 1:1 267 200) as an inset. The maps were published by Goldfields of Matabeleland, Ltd.
After serving in the Anglo-Boer War (1899-1902) Espin was admitted as a land surveyor in the Transvaal Colony in June 1904. In the same year he became a member of the Institute of Land Surveyors of the Transvaal (incorporated in 1904). His address around 1905 was Grenfell Camp, near Louis Trichardt, but by 1909 he was living in Bulawayo. In 1911 he passed the Law Certificate Examination of the University of the Cape of Good Hope, thus qualifying as an attorney. He set up practice in Grahamstown with his brother, Cyril Espinelle Espin, in the firm W. Espin & Cyril E. Espin, attorneys and notaries.