Why too few hulls drive the Royal Navy toward larger ships

Why does the Royal Navy pursue very large carriers and potentially cruiser-sized Type 83 destroyers?

Because governments often promise a small fixed number of hulls, pushing the Navy to maximize each ship rather than trade size for a larger fleet.

The Queen Elizabeth-class carriers were a response to a political ceiling of two hulls. The Navy had considered more numerous smaller carriers, but once only two were funded it chose the largest useful option. Similar pressure is anticipated on the Type 83 replacement for the six Type 45 destroyers. If the fleet again receives too few hulls, each design must carry as much capability as possible because no later quantity increase can be assumed.