Why the Royal Navy did not standardize one dual-purpose gun

Why did the Royal Navy use several dual-purpose gun calibers instead of standardizing like the US Navy?

Changing requirements frustrated repeated standardization attempts, while wartime ships often had to use whatever suitable guns were already available.

The Royal Navy attempted several times to settle on a standard dual-purpose caliber, but different weapons offered different advantages as requirements evolved. During the Second World War, immediate availability also mattered: many ships received guns already held in storage rather than an ideal newly manufactured standard weapon. A caliber that suited a destroyer did not necessarily provide the weight, handling, or anti-aircraft performance wanted in a cruiser or battleship. The resulting variety was therefore the product of changing programs, ship roles, and production realities, not simply a failure to recognize the benefits of standardization.