Why Royal Dockyards stopped building capital ships

Why did the Royal Navy stop using Portsmouth and Devonport for capital-ship construction?

There were too few capital-ship orders to justify the capacity, while commercial yards could bridge naval work with large merchant construction.

The Royal Navy was no longer ordering enough capital ships to keep every state yard's largest facilities continuously productive. Portsmouth and Devonport could therefore concentrate on cruiser work rather than carrying the standing cost of battleship construction capacity. Commercial yards were better able to preserve large-hull skills between naval orders by building liners and major merchant ships. The answer frames dockyard specialization as an industrial-workload decision, not as proof that the Royal Navy had forgotten how to build capital ships.