What difference would a 28-knot Nelson-class battleship make?
Short answerIt could catch German fast capital ships, threaten Scharnhorst-class survival, and trigger larger-gun responses in both the Bismarck and King George V programs.
NotesUsing the Nelson class's unused displacement to reach 28 knots would remove the speed margin on which Scharnhorst and Gneisenau depended. A faster Rodney could catch them during an early-war sortie and bring nine 16-inch guns into an engagement they historically escaped. Losing a German ship that early could alter the urgency, armament, and deployment of Bismarck and Tirpitz, perhaps forcing development of a German 16-inch weapon. British knowledge of that response could then push the King George V class toward its own nine-gun 16-inch layout, while Tiger and modernized battlecruisers broadened the Royal Navy's fast-capital-ship force.