Walter Charles Cross Pakes qualified as a licentiate of the Royal College of Physicians (LRCP) of England and a member of the Royal College of Surgeons (MRCS) of London at Guy's Hospital Medical School in 1895 and obtained the Diploma in Public Health (DPH) at Cambridge in 1896. He was furthermore elected a Fellow of the Chemical Society (FCS). He served in junior positions at Guy's Hospital before being appointed as lecturer in bacteriology there in 1898. At the same time he was professor of hygiene at Bedford College for Women. His first paper, "An apparatus for counting colonies", was published in the Journal of Pathology and Bacteriology in 1897. Several more papers by him appeared during the next five years, including one on bacteriology and public health in the British Medical Journal (1900), "A note on the organisation and conduct of plague laboratories" (ibid, 1901) and three joint papers with W.H. Jollymain* in the Journal of the Chemical Society in 1901. He also wrote Science of hygiene; a text-book of laboratory practice (London, 1900, 380 pp), of which revised editions appeared in 1912 and 1921.
In 1902, shortly after the conclusion of the Anglo-Boer War (1899-1902), the British authorities of the Transvaal Colony appointed Pakes as superintendent of a newly established government laboratory in Pretoria, the main task of which was to perform clinical and bacteriological studies on rats to check for the presence of plague. His wife and child followed him to South Africa. In 1903 the laboratory was transferred to Johannesburg and established on the site that would later be occupied by the South African Institute for Medical Research. The laboratory was under the control of the Medical Officer of Health for the Transvaal, Dr George Turner*. The staff consisted of Pakes, Jollyman* and Frank H. Joseph*, with four technicians who did mainly medico-legal work. Pakes's official position was that of government analyst and bacteriologist.
Pakes contributed a paper to the Journal of the Chemical, Metallurgical and Mining Society of South Africa in January 1904 on "Ankylostomiasis: A forewarning", in which he reported the first occurrence of hookworm disease on the Witwatersrand. In March 1904 plague broke out in an Indian township of Johannesburg. Pakes was appointed medical officer of health to the Rand plague committee to combat the disease and succeeded in bringing it under control within a few months. He reported on the work in The Lancet in 1904. That same year he started work on a prophylactic pneumonia vaccine, the so-called "Pakes anti-pneumococci serum", with a grant of £1000 from the Transvaal Chamber of Mines. However, nothing seems to have come of it and in 1905, following conflict between him and Jollyman, he resigned from the laboratory. A paper by him on "The Johannesburg municipal sewage scheme from a biochemical point of view" appeared in the Journal of the Chemical, Metallurgical and Mining Society of South Africa around that time (1905/6, Vol. 6). From 1908 to 1916 he was listed in the General directory of South Africa as "Government analyst" in Johannesburg, so presumably he set up in private practice as a chemist and did some work for the government. In December 1909 he was appointed medical superintendent of the Leper Hospital of the Orange River Colony at Sydenham, Bloemfontein, while his laboratory in Johannesburg may have continued work without him. He later returned to the United Kingdom and settled at Nuneaton, Warwichshire.
Pakes was an early member of the South African Association for the Advancement of Science, served as joint secretary of its Section B and as a member of its Publication Committee for 1903/4, and as a member of council for 1904/5. He became a member of the Chemical, Metallurgical and Mining Society of South Africa in 1903 and during 1904-1906 served on its council and publication committee.