If the Queen Elizabeth class made only 21 knots

How would battleship evolution change if the Queen Elizabeth class were 21-knot ships with ten 15-inch guns?

Britain would probably order a separate battlecruiser immediately, and the larger speed gap might cause treaties to preserve battleships and battlecruisers as separate categories.

A slow Queen Elizabeth would not combine battle-line power with fast-wing duties, so another ship would have to fill the battlecruiser role. Fast battleships might still emerge by World War II, but Hood could instead become the model for a distinct treaty battlecruiser category.