The horizontal protection over the magazines consisted of three layers with a total thickness of ; the weather deck consisted of 1.25 inches of Ducol (D) steel, the main armoured deck was of non-cemented steel armour thick over a 0.5-inch D steel deck and above the shell rooms there was another 1.5-inch splinter deck. The powder magazines were below the shell rooms for added protection, a practice that was begun with the "Nelson"-class battleships. The weatherdeck thickness was the same over the machinery spaces but there the main armoured deck was reduced to over a 0.5-inch D steel deck. The main armoured deck was continued forward of the forward armoured bulkhead and gradually reduced from full thickness to 2.5 inches, while aft of the after magazines an armoured turtle-back deck covered the steering gear with 4.5–5 inches of armour whilst also providing protection along the waterline.