He was born in Dunedin, educated at the University of Otago, and joined the Public Works Department in 1878 as surveyor and civil engineer. He moved to the WMR as Resident Engineer, then Chief Engineer and Locomotive Superintendent. The WMR was taken over in 1908 and became part of the New Zealand Government Railways.
In 1909 he was appointed Engineer to the Wellington Harbour Board, retiring as Chief Engineer and Ganeral Manager in 1932. His son Donald Marchbanks (1901–1987) succeeded him as WHB Chief Engineer.[1][2][3]
He was a foundation member of the New Zealand Institution of Civil Engineers and was Honorary Treasurer of the New Zealand Institution of Engineers for many years.