A fused jacket is made by bonding a stiff interlining to the face cloth with heat-activated glue. It is fast, consistent and cheap, and for the first season it can look entirely convincing.

The problem is that cloth and adhesive expand at different rates. Steam, rain and solvent cleaning gradually break the bond, and once it separates you see bubbling across the chest and lapel. No pressing will bring it back, because the failure is structural.

A floating canvas has no glue to fail. Horsehair and wool are stitched to the cloth loosely enough to move independently, which is why the chest of a canvassed jacket softens and shapes to its wearer instead of stiffening away from him.

There is a practical test. Pinch the cloth between the buttonhole and the lining and rub gently; if you can feel a third loose layer sliding between them, the jacket is canvassed.