The analysis separates hindsight from what British designers could know when photographs and tightly guarded intelligence were their evidence. Even if they identified an 18-inch gun, they might not know whether its barrel was 46, 48, or 50 calibres long, and those possibilities implied different performance. A responsible design staff could not assume the Japanese weapon was less efficient than Britain's own large guns. The safer planning case therefore treats Yamato's armament as highly effective and adds protection to a British response. In practice, uncertainty about the enemy gun would drive extra displacement, armour, and cost.
Notable Point · 58:38-1:01:02
How uncertainty about Yamato drives worst-case protection
British designers would have to turn incomplete intelligence about Yamato's guns into conservative assumptions about range, penetration, and armour.