Macarthur-Onslow, James William, 1867 – 1946

James William Macarthur-Onslow (1867-1946), soldier, grazier and parliamentarian, was born at 'Camden Park', NSW, son of Arthur Alexander Walton Onslow (1833-1882) and his wife Elizabeth (1840-1911), daughter of James Macarthur and his wife Emily. Arthur A.W. Onslow was the son of Arthur Pooley Onslow of the East India Co. and his wife Rosa Roberta, daughter of Alexander Macleay (1767-1848). After the death of Arthur A.W. Onslow, Elizabeth changed the family name in 1892 to Macarthur-Onslow.

Macarthur-Onslow was educated at Sydney Grammar School and Trinity College, University of Cambridge where he graduated Bachelor of Arts and Laws (1890). He returned to Australia in 1891, and in 1892 was commissioned captain in the Camden squadron of the NSW Mounted Rifles. He undertook special training in India and served with the 1st Battalion, Kings Royal Rifle Corps in India. He was promoted to major in 1896 and lieutenant-colonel in 1898. He served in South Africa 1900 to 1901 and was awarded the Queen's medal with clasps. He was ADC to the Governor General (1902-1909, 1917-1920). Macarthur-Onslow was promoted to colonel in 1907 and between 1915 and 1917 made several journeys between Australia and the Middle East where the AIF were serving. He retired in 1925 with the rank of major general.

Macarthur-Onslow was a supporter of Sir Edmund Barton's National Federal Party and was elected to the NSW Legislative Assembly for the seats of Waverley (1907-1913), Bondi (1913-1917) and Eastern Suburbs (1920-1922). He was a nominated member of the NSW Legislative Council (1922-1934).

Macarthur-Onslow was, along with his brothers and sister, a director of Camden Park Estate Pty. Ltd., a company established by his mother for the purpose of administering a dairying complex on the Camden Park estate. In 1826 Macarthur-Onslow's great-grandfather Alexander Macleay (1767-1848) was granted land at Elizabeth Bay on which he built Elizabeth Bay House. Macarthur-Onslow inherited Elizabeth Bay House from his great-uncle Sir George Macleay.[ref:ADB 10]