The Diadem class cruiser was a class of "First-Class" protected cruiser built for the Royal Navy during the 1890s that served in the First World War. The class consisted of eight ships, built at a cost of around £600,000 each. They were considered "good sea boats" but criticised for their lack of a heavy calibre main armament, bulky unprotected sides, average speed and lack of manoeuvrability despite being considered large ships when completed. They were the last British first class protected cruisers; the armoured cruiser taking the large cruiser role in future."