Why Britain did not press for an 18-inch treaty limit

Why did Britain not argue for an 18-inch gun limit when it had 18-inch guns in service?

It preferred a limit that protected its existing lead and avoided prompting every navy to build new battleships.

Britain had little incentive to demand 18-inch guns after its own 18-inch mounting experience disappointed. The weapons actually placed in service had not fulfilled the promise of the designs Britain had considered. An 18-inch treaty limit would also have encouraged every major navy to start a new generation of battleships. Keeping the limit lower let rivals finish older design lines while the Royal Navy preserved the advantage of possessing the two most modern battleships.