Chief engineer
Darbyshire accepted the appointment as Chief Engineer of the Railways on the condition that he retained his substantive appointment as District Surveyor Williamstown and could return to that at any time (See letter of 28 May 1856 referred to above.). He acted as Deputy Surveyor General from May to July 1857 while holding the position of Chief engineer. He returned to his position as District Surveyor on resigning his position as Chief Engineer Railways.