William M. Power, veterinarian and politician, was the son of Michael Power and his wife Anastasia Hayes. He studied at Waterpark College (in the city of Waterford, Ireland), qualifying as a member of the Royal College of Veterinary Surgeons (MRCVS) in 1896. After practising as an assistant in Dublin for some time he came to the Natal Colony in 1899 and entered the civil service as a temporary district veterinary surgeon in June that year. During the Anglo-Boer War (1899-1902) he served as a veterinarian in the Natal Carbineers and in 1906 took part in the suppression of the Bambata Rebellion. In 1902 he married Mary G. Carroll, with whom he had three sons and three daughters.
Power served as district veterinary surgeon in Ladismith (November 1901-1902), Ixopo (1902-1905), Richmond (1905) and Paulpietersburg (1905), and after a short time as acting principal veterinary surgeon at Pietermaritzburg (1905-1906), in Louwsberg (1906). On 1 November 1907 he succeeded S.B. Woollatt* as principal veterinary surgeon and chief of the Veterinary Division in the Department of Agriculture of Natal. The name of his post was changed to chief veterinary surgeon of Natal in May 1910. After the formation of the Union of South Africa in 1910 he was appointed in January 1912 as senior veterinary surgeon for Natal in the Union Department of Agriculture, a post he held until his retirement in 1928.
Power contributed two articles to the Natal Agricultural Journal, one on "Cattle dipping" (1908, Vol. 11, p. 322), the other on "Epizootic Lymphangitis" (1909, Vol. 13, pp. 539-541). In 1909 he became a foundation member of the Natal Veterinary Medical Association, having already joined the Transvaal Veterinary Medical Association earlier that year. In 1920 his membership was transferred to the newly created South African Veterinary Medical Association. He became a member of the Royal Agricultural Society in Pietermaritzburg in 1910, served as its president from 1929 to 1934 and was then made an honorary life president.
After his retirement from the Department of Agriculture Power took up private practise. In 1931 he was elected to the Provincial Council of Natal, where he represented the Pietermaritzburg suburbs until 1947. From 1933 to 1945 he served on the Natal Executive Committee and in 1935 and 1937 chaired a commission which investigated the establishment of game reserves in the province. He was particularly interested in the Hluhluwe Game Reserve, wild flower reserves and the protection of fresh-water fish. From 1939 he was chairman of the Zululand Game Reserves and Parks Board and (from 1947) its successor, the Natal Parks, Game and Fish Preservation Board, until 1950. He served, among others, as a member of the Land Tenure Advisary Board (1947-1951), the Historical Monuments Commission, the Veterinary Services Commission, and the Broome Commission on Natal Indians.