David Milne was born at 121 Hawkhill, Dundee, Scotland on 9 August 1881 and was articled in the office of John Murray Robertson (1844-1901) in Dundee from 1898 to 1902. He then moved to London and worked as an assistant in the London County Council Architects' Department; to Leonard Aloysius Scott Stokes (1858-1925); to William George Robert Sprague (1863-1933); and to Edwin Otto Sachs (1870-1919). He also attended the Architectural Association Schools. and Royal Academy Schools in London He qualified as an architect in 1908 and was elected an Associate of the Royal Institute of British Architects (ARIBA) later that year.
In 1910, with James William Herbert (1881-1961) he entered a competition to design the new Museum of Wales in Cardiff. They came third. Their designs are illustrated in British Competitions in Architecture vol. 3, nos. 34-35, March 1911 (pp. 273, 293-296)
It is not known if Milne and Hepburn had a formal partnership or if they just collaborated on this project. By 1914 Milne had moved to Doncaster, Yorkshire where he was in practice at 8 Priory Place, Doncaster.
Milne's address was given as 3 Queen Square Place, London in 1908; 55 Southampton Row, Bloomsbury, London in 1911; and 8, Priory Place, Doncaster, Yorkshire in 1914 and 11 Lawn Road, Doncaster, Yorkshire in 1917. He served in the Army Cyclist Corps during World War One and was killed in action in France on 21 [1 or 28 - sources differ] September 1918
Directory of British Architects 1834-1914. Compiled by Antonia Brodie, et al. Volume 2: L-Z. London; New York: British Architectural Library, Royal Institute of British Architects/Continuum, 2001
‘Obituary’. Royal Institute of British Architects Journal vol. 26, June 1919 p.196