What 42,000 tons could add to the Nelson design

How would a 42,000-ton treaty limit change Nelson and later battleship development?

It could buy Nelson much greater speed or firepower and would push every later treaty power toward larger, more heavily armed battleships.

An extra 9,000 tons opens several design paths. Nelson could reach about 28 knots, add a fourth triple 16-inch turret, or combine greater speed with a much larger 14-inch battery. A sixteen-gun version would bring both a heavy broadside and the practical problem of seeing the target through its own shell splashes. The same 42,000-ton ceiling would shape the King George V and Iowa classes, then force Japan to answer a much more powerful Anglo-American standard. The counterfactual therefore changes the treaty system and its competitive responses, not one British design in isolation.