Battleship turrets as Gibraltar batteries

How many surplus 13.5-inch naval turrets would be needed to close the Strait of Gibraltar?

Four or five twin turrets would be sufficient, or six for an especially powerful battery, controlled by directors on the Rock with backups below.

The proposed installation uses complete twin turrets rather than individual guns, preserving a high concentration of fire. A director on the Rock would exploit the commanding elevation, while lower backup positions would remain available when fog obscured the summit. The exchange shows how scrapped warship armament could extend the defensive value of a fleet long after its original hulls were retired.