Born in Ayrshire, Duncan attended the Ardrossan Academy in Ardrossan, North Ayrshire and was educated at the University of Birmingham where he obtained a BCom in 1985. He later worked as a business and communications consultant for Mackays Stores Ltd from 1985 to 1988 in addition to running the family textile business - John Duncan &amp; Son from 1988 to 2000. In September 1997, he appeared as a member of the audience during a Scottish Television debate about the devolution referendum, and spoke opposing the establishment of a Scottish Parliament. Duncan later stood for election to the very parliament he initially opposed.