Where a Royal Navy expansion could find sailors

How many British merchant sailors could support a Royal Navy buildup over several years?

The Royal Navy would need to look mainly to its reserves, not the merchant marine, whose relatively small and officer-heavy workforce is essential to keeping commercial shipping operating.

Britain's merchant marine was not a large pool of easily transferable personnel. Its workforce was relatively small, highly trained, and weighted toward officers and specialist technicians. Moving many of those people into naval service would weaken the commercial fleet that national sea power also depended on. Reserves therefore offered the more realistic starting point for expansion. Fleet growth had to account for the wider maritime labor system rather than treating sailors as interchangeable manpower.