 The turret faces were fifteen inches thick while their sides ranged from 11 to 12 inches ( 279 to 305 mm ) in thickness , and the roof was five inches thick . The barbettes had a maximum of twelve inches of armour , but were reduced in thickness in stages below decks , although the outer faces of ' A ' and ' Y ' barbettes were considerably thicker below decks than the other barbettes . The conning tower armour was nine to eleven inches thick , and it was the largest yet fitted to a British capital ship as it weighed 600 long tons ( 610 t ) . The primary fire @-@ control director atop the conning tower was protected by an armoured hood . The face of the hood was six inches thick , its sides were two inches thick , and its roof was protected by three inches of armour . A communications tube with six @-@ inch sides ran from the conning tower down to the lower conning position on the main deck . The three torpedo bulkheads were 1 @.@ 5 inches ( 38 mm ) , 1 inch ( 25 mm ) and .75 inches ( 19 mm ) thick . 
