He later retired from professional practice and pursued his interest in the history of civil engineering. He also studied under Roderick Weir Home, Professor of History and Philosophy of Science at the University of Melbourne. Harper became a member of the National Trust expert historic bridges committee in 2000, continuing on the committee up to its folding in 2012.National Trust of Australia, (Victoria) Annual Report 2007 He has been active in nominating National Engineering Landmarks Nomination NATIONAL ENGINEERING LANDMARK Dartmouth Dam and Spillway Prepared by Brian Harper & Bruce Cole and also became a member of the exclusive Wallaby Club in 2008.Biographical Entry, The Wallaby Club 2011, Last modified: 5 July 2012
