The appointment was made by Premier of Victoria Albert Dunstan on the advice of the Metropolitan Police Commissioner Sir Philip Game—a former Governor of New South Wales.

Dunstan ordered the inspection after the controversial resignation of the previous Chief Commissioner Thomas Blamey amid public allegations of widespread corruption within the force.

[1] Duncan presented two reports to the Victorian government which recommended a range of reforms, including detective training and the use of forensic science and changes to the promotion system and the deployment of personnel.

[1] Once appointed, Duncan began the task of dealing with "entrenched bad practice, poor leadership, maladministration and corruption.

[1] Duncan was active in the "Boy Scouts' Association, Melbourne Rotary, YMCA, the Royal Humane Society, the National Fitness Council and the State Relief Committee.