Why wartime seizures multiplied Royal Navy gun types

Why did the Royal Navy operate so many different heavy-gun types in closely related calibers?

Many came with foreign warships seized from British yards, and existing ammunition lines made retaining those weapons cheaper and faster than rebuilding the ships.

The Royal Navy did not deliberately seek every gun type it inherited during the world wars. British yards built warships to foreign customers' specifications, and the navy took over completed or nearly completed ships when war interrupted delivery. Replacing their weapons would require major reconstruction, while the same export contracts had already established ammunition and supplier lines. Keeping the existing guns was the fastest practical way to turn those hulls into wartime strength, even at the cost of long-term standardization.