William Langston Newnham was born in Christchurch on 14 October 1888, the son of Charles Langston Newnham, a journalist, and his wife, Eliza Friar. He attended Timaru Boys’ High School, then joined the Public Works Department (PWD) in 1908 as a cadet. He was briefly a student of engineering at Canterbury College in 1914, but did not complete a qualification. On 24 April 1916 at Napier, he married Ethelwyn Frances Smallbone. She died of pneumonia in 1919, and on 6 December 1920 he married Margaret Thornton in Christchurch; they were to have two sons and a daughter.
Newnham enlisted in the army in November 1916, but was discharged on medical grounds in January 1918 without having served overseas. He was then assigned by the PWD to work on the Napier–Gisborne railway. For several years his primary professional experience was with railway construction: on the survey for the Remutaka deviation, the North Auckland main trunk, the Stratford–main trunk link and the Otira rail tunnel in the South Island.
In 1920 Newnham was elected a member of the New Zealand Society of Civil Engineers, skipping the usual grade of associate member. His post at the time was described as assistant engineer. Based in Wellington, he was engaged on the Tawa Flat railway deviation in 1927, working with a younger colleague, A. F. Downer; they wrote a joint paper on the work completed to that time. For a later paper, Newnham was given a Fulton special award.
The Engineers Registration Act 1924 was designed to require minimum qualifications and professional standards for engineers responsible for local authority works. Newnham was appointed the first registrar to the Engineers Registration Board and began his long association with the department’s chief engineer, F. W. Furkert, one of the act’s main proponents. He remained registrar until 1939, when he was appointed to the board (of which he was chairman in 1943), and remained in the post until his resignation in 1965. In his 40 years’ association with the board he was probably the single most important influence on its work.
Newnham was promoted to designing engineer with the PWD in 1929 and inspecting engineer in 1936. He served as engineer in chief and under-secretary from 1941 until 1943. The two functions were separated that year, and until 1946 Newnham was engineer in chief. He served on many committees, including those dealing with the revision of building standards following the Hawke’s Bay earthquake of 1931. He was also president of the New Zealand Institution of Engineers in 1945–46. During the Second World War Newnham was director of fortifications and works (from March 1941) with the honorary rank of colonel. He formally enlisted in April 1942 and was appointed director general of engineering services, commanding the New Zealand Defence Engineer Service Corps.
Newnham retired in 1946, at the age of 57, following the restructuring of the PWD. In retirement he served on the Main Highways Board and continued as foundation chairman of the Soil Conservation and Rivers Control Council (1942–57). He was made a CBE in 1952.
Probably William Newnham’s most important legacy is the effect he had on the organisation and conduct of the engineering profession in New Zealand, and on the preservation of its heritage. He served for many years on the NZIE’s education committee. Among the most important of many initiatives was his recommendation in 1935 that Canterbury University College’s School of Engineering broaden its curriculum by including subjects such as economics and industrial psychology. In retirement he completed the manuscript for Furkert’s book, Early New Zealand engineers , which appeared in 1953, over four years after Furkert’s death. Newnham’s own book, Learning, service, achievement (1971), contains much detailed and otherwise inaccessible information about the engineering profession in New Zealand between 1914 and 1964. The book was written for the jubilee of the foundation of the NZIE, but was much delayed because Newnham was ill.
William Newnham’s stature in the engineering profession is recognised in the W. L. Newnham Lecture, the principal invited lecture delivered at the annual conference of the institution. He died in Rotorua on 15 March 1974, survived by his three children; his second wife had died in 1956.