 Two armoured cruisers of a new design , Duke of Edinburgh and Black Prince , the latter named for Edward , the Black Prince , were ordered for the Royal Navy as part of the 1902 – 03 Naval Estimates . They were the first ships to be designed for the Royal Navy under the supervision of the new Director of Naval Construction , Sir Philip Watts . The new design was significantly larger than the previous Monmouth and Devonshire @-@ class cruisers , mounting a heavier main armament of six 9 @.@ 2 in ( 234 mm ) guns in single turrets . 
