The individual ship histories end by asking whether the Diadem class was a failure and answering that the ships were useful. Their structural problem was the awkward gap between inexpensive second-class protected cruisers and the fleet's most powerful armoured cruisers. At roughly 11,000 tons, they illustrate the recurring scale needed to combine endurance, seakeeping, protection, and useful armament in an all-round cruiser. That much capability also made the type too expensive to defend through the usual argument that a cheap ship could accept obvious omissions. This conclusion leads into Britain's decision to abandon a distinct first-class protected-cruiser tier.
Notable Point · 1:06:32-1:08:19
The recurring 11,000-ton problem of a middle-tier cruiser
Diadem's 11,000-ton size illustrates why a useful all-round cruiser repeatedly lands in the expensive and politically awkward middle of a fleet.