Douglas was born in a small village in Scotland, not far from Loch Lomond. He went to an excellent village school and he studied geography and archaeology at the University of Glasgow.
Having been Editor of various stamp magazines such as Stamp Collecting, Philatelic Magazine and The British Philatelic Bulletin, Douglas Muir joined the National Postal Museum as Curator, Philately in 1988. He has remained in that job ever since, now for the independent educational charity, the British Postal Museum & Archive.
He is the author of several books including Postal Reform & the Penny Black: As New Appreciation (1990), A Timeless Classic: The Evolution of Machin's Icon (2007) and most recently George V and the G.P.O.: Stamps Conflict & Creativity (2010).
Douglas is also a signatory of the Book of Scottish Philatelists.