The heavy cruiser emerged as a treaty category

When did the Royal Navy begin looking for distinct light- and heavy-cruiser types?

Cruiser design never stopped evolving, but the formal heavy-cruiser definition arrived with the London Naval Treaty, leaving earlier ships to be understood through different contemporary categories.

The Royal Navy did not wake up one year and begin a wholly new cruiser search. Designs evolved continuously as missions, weapons, and displacement changed. The London Naval Treaty supplied the formal distinction that made heavy cruiser a recognized category. Before that agreement, ships later described through the treaty lens could be treated as large light cruisers or by other contemporary language.