 Intended to resist the impact of a 1 @,@ 000 @-@ pound ( 450 kg ) armour @-@ piercing bomb dropped from a height of 14 @,@ 000 feet ( 4 @,@ 300 m ) , Vanguard 's deck protection was identical to that of the King George V class . It consisted of six @-@ inch non @-@ cemented armour over the magazines that reduced to 5 inches ( 127 mm ) over the machinery spaces . The armour continued forward and aft of the citadel at the lower @-@ deck level . Forward it tapered in steps from five inches down to 2 @.@ 5 inches near the bow . Aft , it protected the steering gear and propeller shafts with 4 @.@ 5 inches of armour before tapering to a thickness of 2 @.@ 5 inches near the stern . Unlike the Germans , French and Americans , the British no longer believed that heavy armour for the conning tower served any real purpose given that the chance of hitting it was very small ; Vanguard 's conning tower was therefore protected with 3 inches ( 76 mm ) of armour on the face and 2 @.@ 5 inches on the sides and rear . The secondary conning tower aft had 2 inches ( 51 mm ) of armour on its sides . 
