What Benbow’s 18 inches of armour can and cannot mean

Benbow’s two-to-three-inch armoured deck and exceptionally thick belt make her look like a floating block of steel. Her armour material was less effective than later armour, so thickness alone cannot establish protection quality across eras. Even with that qualification, an eighteen-inch belt sounds formidable beside the thirteen-inch belt of the Queen Elizabeth class and HMS Warspite. The comparison still involves a design trade-off because carrying Benbow’s thickness of armour at Queen Elizabeth speed would have required a substantially larger ship.