William Riddet was born on 16 March 1896 in Dalry, Ayrshire, Scotland, one of five sons and two daughters of Lillias Tweed Miller and her husband, Robert Lang Riddet, a farmer who was active in kirk and community affairs. William went to Dalry higher grade public school and the Irvine Royal Academy where he showed early promise academically. During his school days, and for some years afterwards, he worked on the family farm.
Riddet entered the West of Scotland Agricultural College as a dairying and agricultural student in 1914. After completing a year of study he volunteered for war service, joining the Royal Army Veterinary Corps in May 1915. From August 1917 he served with the 4th Battalion, Royal Scots Fusiliers, seeing action in Palestine, France and the Rhineland. He was demobilised in 1919 with the rank of captain.
After the war Riddet fulfilled his earlier academic promise, gaining honours in both the national diploma of agriculture (first in the United Kingdom) and the national diploma in dairying. He won numerous prizes and graduated BSc (Agric.) from the University of Glasgow in 1923. From 1921 to 1925 he held positions with the West of Scotland Agricultural College organising agricultural education and extension in various shires. He also gained practical experience of milk testing as a recorder for the Arran milk record society. In 1924 he was appointed a lecturer in dairying at the college.
In May 1925 Riddet was appointed to the Logan Campbell chair of agriculture at Auckland University College, New Zealand. Tertiary education in agriculture was in disarray when he arrived. Canterbury Agricultural College (at Lincoln), although established since 1880, was not perceived to be meeting the need for trained agriculturalists, and the two North Island colleges of the University of New Zealand – Auckland and Victoria – were making parallel but separate bids to fill the niche. Geoffrey Peren had been appointed in 1924 to the newly endowed Walter Clarke Buchanan chair of agriculture at Victoria, and Riddet was soon convinced of the good sense of a joint venture. While the politicians negotiated the establishment of a new agricultural college, Peren and Riddet gave it their united support.
At the request of the university senate the two prepared a revised syllabus for agricultural teaching, which was completed in December 1925. It closely foreshadowed the four-year bachelor of agricultural science degree subsequently taught at Massey Agricultural College. The primary emphasis was on providing a firm basis of scientific principles from which to teach the more applied courses in agriculture. The rigorous academic programme coupled with a major requirement for practical work would prepare graduates to enter all sectors of the agricultural industry.
In 1926 Riddet and Peren travelled throughout the North Island inspecting potential sites for the new agricultural college. They chose the Batchelar property at Palmerston North. The college was formally established on 11 September 1926 and Riddet was appointed to the foundation chair of agriculture. In 1927 he was appointed director of the newly established Dairy Research Institute.
Riddet was now responsible for teaching dairy husbandry and technology and directing research into the many problems confronting the dairy industry. At a time when scientists were treated warily, he was able to talk with both dairy farmers and dairy factory managers. He was renowned for his enthusiasm, energy and endless supply of new ideas. In the years up to the Second World War his imprint is clearly seen in a wide range of projects undertaken at Massey. Technical publications bearing his name deal with pasture management, cow nutrition and milk composition, flavour defects in milk and dairy products, butter boxes and cheese quality. In 1938 he came up with the idea of using electric fences for pasture rationing, a strategy that became identified with New Zealand dairy farming. He was an enthusiastic champion of the active marketing of dairy products, herd testing, milk quality tests, soil drainage and many other technical innovations.
William Riddet's most important contribution to the dairy industry was to promote an acceptance of research as a means of solving problems. Under his directorship the institute made a number of major advances that placed it firmly amongst the leading dairy research establishments in the world. Particularly noteworthy was H. R. Whitehead's work on single-strain starters and bacteriophages, which largely eliminated openness in cheese – a problem that had long perplexed and severely threatened the cheese industry. Equally important were F. H. McDowell's studies on the factors affecting the processing characteristics of milk.
Riddet instigated the highly successful Massey dairy farmers' conference, a unique forum for scientists and dairy farmers to share new ideas and technology. He also promoted the dairy factories' managers' week, equally successful in drawing together researchers and factory managers. He was an active member of the New Zealand Dairy Science Association, the New Zealand Society of Animal Production, the New Zealand Grassland Association, the New Zealand Institute of Agricultural Science, and the Rotary Club of Palmerston North, among other organisations. He was a founding member of several and held high office in many. He was also a trustee of St Peter's School, Cambridge.
Riddet received many awards and honours. A grant from the Carnegie Corporation of New York allowed him to visit North America and Europe in early 1936. He was awarded the highly prestigious gold medal by the Society of Dairy Technology, London, in 1953, and was made a CBE in 1954.
William Riddet and Mary Stuart McLean had married in Sydney on 27 December 1928. Mary died in 1945, leaving Riddet with two young children. He married Dorothy May Richards on 19 June 1948 at Palmerston North. On 30 December 1958 he died from leukaemia, survived by Dorothy and his two children.
William Riddet was known as 'the Wee Mon', a sobriquet reflecting his Scottish roots and small stature. He was long remembered as an inspiring teacher. Many of his students went on to make valuable contributions to the teaching, research and practice of dairying in New Zealand. Both this, and his own contribution to the industry, mark him as the founder of dairy science in New Zealand.