 At least some of the designs were passed to Admiral John Jellicoe , commander of the Grand Fleet , who pointed out that there was no need for new battleships as the British superiority in numbers over the Germans was substantial , but that was not true for battlecruisers . Germany was known to be building three new Mackensen @-@ class battlecruisers with an estimated speed approaching 30 knots ( 56 km / h ; 35 mph ) and a reported armament of 15 @.@ 2 @-@ inch ( 386 mm ) guns . These ships would be superior to all existing British battlecruisers , and those then under construction ( the two Renown @-@ class and the three Courageous @-@ class ' large light cruisers ' ) were equally fast , but too thinly armoured to compete with them . He also remarked that his experience with Queen Elizabeth @-@ class had persuaded him that an intermediate speed between the battleships and the battlecruisers was of little use ; he suggested that the design should be for either a 21 knots ( 39 km / h ; 24 mph ) battleship or a thirty @-@ knot battlecruiser , preferably the latter . 
