Navy Carriers: We want two or no votes for you, Tories
No frigate on Caribbean drugs patrol? Imagine my concern
So what's the downside? Assuming you haven't spent your whole life in an effort to be a frigate captain?
Really we need a maximum total escort fleet of say 10, as compared to the Navy's current lineup of 23. Savings just in running costs over the next decade would add up to at least £11bn. Then we can save at least another billion-odd in acquisition costs by not buying the last two Type 45s and their dubious missile systems. All this is far and away more than enough to ensure that the second carrier is built, and to give the two ships catapult launch. This in turn would permit the purchase of much cheaper and more powerful aircraft for them, easing the problems caused for the MoD budget by the rising costs and delays facing the F-35B supersonic stealth jumpjet (currently grounded following the discovery of technical snags during flight testing).
All up, such a plan would not only deliver a 2-carrier, 10-escort navy - it would deliver savings on top that would cope with a big chunk of the budget gap caused by the economic crisis and 20 years of stupid management at the MoD by both previous governments.
What's the downside?
Well, we'd no longer be able to provide a frigate or destroyer on patrol in the Caribbean as we now do. A few more consignments of drugs might get through to the USA: RN matelots could no longer expect runs ashore in tropical resorts quite as often. Imagine my concern.
Nor would we any longer be able to keep an escort on station off the Falklands. But there would still be strike jets based there, so Argentina would have no option to invade: and there's also already a separate patrol vessel for keeping an eye on fisheries, oil exploration etc.
Single frigates or destroyers would no longer be able to roam the world in general on "show the flag" cruises whose benefits have always been pretty notional. It doesn't impress a Third-World dictator or oligarchy to see an antisubmarine ship pull into the harbour and give a cocktail party: the only menace it poses is a tiny party of marines (if there are even any aboard) and a helicopter mostly full of sonar equipment - ie no menace at all.
Want to fight some pirates? Send a fleet-auxiliary supply ship with radar-equipped helicopters and embarked troops. It can respond a lot faster to pirate attacks across a wide area than a frigate or destroyer can. (Such a ship - some such ships in particular - are almost pocket heli carriers. They really would scare a dictator or a junta.) Funnily enough, the RN is actually doing this in a small way at the moment against the pirates of Somalia, in an effort which will be at least as effective as sending frigates.