Could Britain field 18-inch guns by 1942?

Could Britain have developed and debugged an 18-inch battleship mounting by 1942?

Probably: existing British large-gun experience and a scaled Lion design offered a plausible accelerated route.

An operational British 18-inch mounting by 1942 is treated as plausible. Britain had experimented with 18-inch weapons since before the First World War and had placed examples in service, even if they were not mature battleship systems. Scaling the Lion class and its turret work into an eight- or nine-gun successor would be quicker than beginning from a blank design. Resource competition with the Army and RAF would still matter once planners expected the next conflict to return to Europe. This is a judgment about technical and industrial plausibility rather than a settled historical design.