Three changes that would make interwar British cruisers formidable

Which three changes would make the Royal Navy's prewar cruiser force genuinely formidable?

Fit 9.2-inch guns, adopt high-pressure steam turbines, and add roughly four inches of armor protection.

The three-part package fits 9.2-inch guns, adopts American-style high-pressure steam machinery, and adds roughly four inches of armor. The larger gun improves striking power, while the machinery raises efficiency and performance. Applying the protection lessons of better-armored County conversions gives those systems a hull able to remain in action. The proposal is formidable because it improves firepower, propulsion, and survivability together rather than maximizing one feature in isolation.