Why Britain lost competitive capital-ship yard capacity

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

Too few capital ships were being ordered to sustain every specialist yard, and later consolidation reduced Britain to poorly competitive, near-monopoly suppliers.

Portsmouth stopped capital-ship construction because Britain was not ordering enough such ships to keep every yard equipped for the work. Civilian yards could spread large-facility costs across liners and merchant ships, while naval yards shifted toward cruisers and other work. Consolidation eventually created suppliers whose facilities could not truly compete for the same contracts. Once government is the sole customer of a monopoly supplier, private ownership may simply add profit to costs the state already carries.