The 4x1 double breasted jacket (a DB with a four button front, only one of which is working) that is frequently seen in photos of the late Duke of Windsor was actually popularized during the 1930's by the man in the photo: Windsor's late brother, the Duke of Kent.
When made properly, the 4x1's two lower buttons are in line with the tops of the side pockets and the two upper, non-working, buttons are keystoned out above them. The spacing between the upper and lower buttons is quite a bit closer than it is on a more conventional 6x2 double breasted.
The 4x1 DB is a great look on men of average stature or less as the longer sweep of the lapel relative to the jacket gives the impression of height. Despite this, the style is usually only available from bespoke tailors today, and even here a man needs to be careful and precise when he is placing the order. I attempted to order two of them within the past year, from two different tailors. I got one jacket that was a 6x2 minus the top buttons and another that was a conventional 6x2. I still do not own a 4x1.
But I intend to continue trying.