Why Nelson kept her 4.7-inch battery

Why did the Royal Navy not replace the Nelson class's 4.7-inch guns with 4.5-inch weapons?

The available 4.5-inch production was already demanded by new capital ships and aircraft carriers, leaving little capacity for a lower-priority refit.

Competing demand explains why the Nelson class did not receive a 4.5-inch conversion. The weapons being produced were required for new capital ships and aircraft carriers. Those programmes took priority over replacing an existing battery on an older battleship. A sound refit proposal could therefore lose to scarce gun and mounting production elsewhere in the fleet plan.