John Flood Nagle was the second of nine children of Albury solicitor Valentine Flood Nagle and his wife Margaret.
Nagle joined the Board of Trustees of the Art Gallery of New South Wales in 1960 and was the board's chair between 1979 and 1983.
He was patron of the Albury-Wodonga Regional Art Foundation for many years and was instrumental in helping Albury Regional Art Gallery acquire significant works by his close friend Russell Drysdale. He encouraged another friend, Howard Daniel, to gift his small but significant collection to the gallery.
Nagel's commitment to the Albury region's artistic aspirations extended to the bequest of part of his private collection, consisting of over 30 artworks, to MAMA, where it complements the larger collection that he so ardently supported.
Artists represented in the private collection include Russell Drysdale, John Coburn, Donald Friend, Margaret Olley, Lloyd Rees, James Gleeson, Rupert Bunny, Wassily Kandinsky and Jacques Callot.