Why the interwar Royal Navy stopped short of 18-inch guns

Why did the Royal Navy not adopt 18-inch guns in the interwar period?

Treaties constrained the choice, while rate-of-fire considerations made 16- to 16.5-inch guns a more attractive practical limit.

Naval-treaty limits governed interwar gun choices, while the Royal Navy placed unusual weight on rate of fire. A 16- to 16.5-inch weapon offered a useful balance between destructive power and the speed at which a battleship could keep shells moving through its loading cycle. The largest technically imaginable gun was therefore less useful than a slightly smaller weapon that could maintain a faster firing cycle.