Sir Walter Armstrong (1849–1918) was born at Hawick, Roxburghshire, on 7 February 1849, the eldest of five children. He was educated at Harrow School and Exeter College, Oxford, where he obtained only a pass degree. On 11 June 1873 he married Jane Emily Rose with whom he had five daughters and at least one son. He established himself as a perceptive art critic and from 1880 began to work for various newspapers and journals including the Pall Mall Gazette, the St James's Gazette and the Manchester Guardian. During the 1880s he began to publish studies on recent British artists and he revised the second volume of Bryan's Dictionary of Painters and Engravers (1889). His growing reputation as an expert in seventeenth-century Dutch painting and eighteenth-century British art meant that his advice was highly regarded.
In 1892 he was appointed as successor to Henry Edward Doyle as Director of the National Gallery of Ireland, a position he held until 1914. During his time as Director Armstrong initiated a number of important changes within the Gallery. Modern museum practices were introduced with pictures systematically cleaned, framed, and glazed. He completely revised the Gallery's catalogue, largely rewriting it to provide a much more detailed and comprehensive account of the Gallery's holdings. He also presided over the gift of Lady Milltown to the NGI which brought with it considerable difficulties. Armstrong became a JP, and was elected an honorary member of the Royal Hibernian Academy in 1899, in which year he was also knighted. He died at his home in Westminster, London, on 8 August 1918