Thomson Wilson Leys was born at Snenton (Sneinton), near Nottingham in Nottinghamshire, England, on 23 April 1850, the son of Hannah Hartley Wilson and her husband, William Leys, a supervisor of inland revenue. Thomson was educated at the People's College, Nottingham. In 1862 his father became involved in the Albertland scheme to found a nonconformist settlement in New Zealand. Subsequently, William and Hannah and their three sons arrived at Auckland on 4 September 1863 aboard the Tyburnia. However, they did not accompany the other settlers north to Port Albert, deciding instead to settle in Auckland.
Thomson Leys was apprenticed as a compositor on the Daily Southern Cross newspaper. A few years later he transferred to the reporting staff, and in 1870 was appointed sub-editor. Ill health led to his resignation, but after a period as a free-lance writer he returned to his chosen career in journalism. In 1872 he became sub-editor of the Evening Star (later the Auckland Star ). He was also the New Zealand representative for Reuter's Telegram Company and for the Sydney Daily Telegraph.
On 6 September 1873, at the home of her parents in Auckland, Thomson Leys married Charlotte Oxley. They were to have three daughters and two sons. One daughter died in infancy and their younger son was killed in an accident in 1897.
When Henry Brett obtained full ownership of the Evening Star in 1876 Leys was promoted to editor, a position he held for 45 years. He was involved with the establishment in 1878 of the New Zealand Press Association, formed in opposition to the existing New Zealand Press Agency. In 1889 Brett made Leys a partner and in 1900 appointed him managing director of the Brett Printing and Publishing Company, which incorporated the Auckland Star, the New Zealand Graphic and the New Zealand Farmer. Leys's business interests also included the Napier Daily Telegraph, the Northern Roller Milling Company and the Auckland Gas Company.
Under Leys's enterprising leadership the Star expanded in size and steadily increased its circulation. By 1900 it had the largest circulation of any paper in New Zealand. Leys was an ardent liberal and friend of leading Liberal politicians, and a supporter of George Grey. In 1892 Liberal premier John Ballance offered him a seat on the Legislative Council, as did Richard Seddon at a later date. He declined both offers, preferring to exert his considerable influence on politics through his journalism. In 1891 and 1897 he represented a syndicate of New Zealand newspapers at conventions in Australia on proposals for federation of the Australian colonies, and possibly New Zealand, and in 1900–1901 was present as an official member of the Royal Commission on Federation.
A man of wide interests, Thomson Leys was involved in many civic and community affairs, particularly those relating to education. His outstanding contribution in this field was the establishment of the Leys Institute, a project initiated by a bequest from his brother, William, and generously endowed by Leys himself. The institute in Ponsonby was officially opened on 29 March 1905. It provided a free library, a reading room, a hall and a recreation room. In 1906 a gymnasium was added and in 1909 the first children's library in Australasia was established. The founders' aim was to promote learning and self-reliance in a non-sectarian environment for the youth of Auckland. As president and trustee Thomson Leys was the driving force behind the institute for 20 years.
At both a local and national level Leys helped to foster the growth of libraries throughout New Zealand, especially in city schools. He was a member and for some time the president of the library committee of the Auckland City Council, and in March 1910 was elected president of the Libraries Association of New Zealand at the association's inaugural conference in Dunedin.
Leys's literary activity extended beyond his newspaper and library interests. He compiled and edited a number of informative books and pamphlets, including the first Auckland provincial almanac, Reed and Brett's almanac (1873–74), and Brett's colonists' guide (1883), and edited the Early history of New Zealand (1890) by R. A. Sherrin and J. H. Wallace. He also published a vivid eyewitness account of the devastation caused by the 1886 Tarawera eruption.
In 1910 Leys was elected to the Auckland Society of Arts committee and from 1912 to 1924 was a member of the Mackelvie Trust, which had been founded on the death of art collector and benefactor J. T. Mackelvie in 1885. Leys was a generous donor of paintings to the Auckland Art Gallery and helped to found the Old Colonists' Museum in 1916. From 1916 to 1924 he was on the Auckland Institute and Museum council, and was one of the judges of the competition designs for the new Auckland War Memorial Museum building in the Auckland Domain. A long-serving member of the Auckland University College council, he was chairman from 1916 to 1920 at a time of great controversy over the relocation of the college, a matter with which he dealt with pragmatism and diplomacy. He also gave many years of service to the Auckland Centre of the Workers' Educational Association.
In January 1912 his wife, Charlotte Leys, died. On 29 December 1913, at Auckland, he married Avice Mason Williams, a librarian and daughter of Mary and Alexander Williams. In the last 10 years of his life Thomson Leys travelled extensively. He was with the British press delegation that visited Germany before the First World War and in 1920 represented New Zealand at the Empire Press Union conference in Canada. He was awarded an honorary LLD by McGill University, Montreal.
Thomson Leys died at Auckland on 27 September 1924, and was buried at Purewa cemetery. A man of tremendous drive and vision, and an astute businessman highly respected for his integrity and organisational abilities, he had given over 50 years of service in the fields of journalism, education and the arts. The Leys Institute is a lasting memorial to his philanthropy.