To believe that frigates are as cost-effective as carriers, you pretty much have to accept that the Earth is flat
Italy or a future non-carrier RN, wishing to send warships - or protect any sea lanes! - beneath the footprint of even a poxy little foreign air force would be dependent on the USN or France to guarantee their safety. You can't protect sea lanes with destroyers and frigates: even the £1bn+ Type 45 destroyer can only defend a piece of sea perhaps fifty miles across from low-flying or surface attackers*, as it is on the surface and thus its radars cannot see very far.
Again in the case of non-nuclear submarines (the only kind we are ever likely to fight) the primary weapon is airborne radar scanning huge swathes of ocean. This forces the boats to submerge and pull down their masts - and thus in the case of conventionally-powered subs it blinds them, cuts off their comms and pins them to the map.
Needless to say, many Royal Navy officers, who are mostly not aviators and not marines, passionately want to believe that none of this is true. If it weren't it would make sense to spend taxpayers' money on lots of surface warships, and there would be many more chances for an officer to be captain of one - so, there would be hugely improved promotion prospects.
But as long as the world is round, radar will continue to see hugely further from an aircraft than from a ship. Only if the Earth were flat would an escort flotilla beyond the very smallest be worth having: and it isn't flat.
Everything is still to play for here, and one has to remember that the armed services often put forward savings plans - and leak them to the media, as we see here - in the hope that politicians and public will instinctively recoil. Such a ploy used to be known as "doing a Royal Yacht", as the RN was formerly known for offering up HMY Britannia for cuts in the belief that no politician would dare call their bluff. (An erroneous belief, as it eventually turned out.)
"Oh no - two carriers means a smaller navy than Italy! Scrap them now!" - that's what the wouldbe frigate captains of the RN are hoping people will say, on reading the Telegraph today.
But we here on the Reg naval desk say that the only problem with this plan is it doesn't go far enough. Get rid of another escort or two and save HMS Ocean along with the carriers, we say. Fit them both with catapults and fill them with lovely cheap F-18s, and fob off the Pentagon (and the US anti-F35 lobby) by staying in the F-35 test programme and saying that we'll buy some F-35Cs at some undetermined future point, when they have become cheap and our current financial woes are in the past.
We say again: Come on, Cameron, Fox, Osborne. You know you want this. When the next crisis blows up somewhere, you know you want to be able to say "Blighty will have a carrier on station shortly, merchant shipping can proceed in peace, we may very well land troops if we feel like it", and feel happy in the knowledge that no tinpot local junta or oligarchy with a handful of jets (or "stealth flying boats", or diesel submarines) can stop you. Nor need you worry what America may do or not do, whether you can get use of a local airbase from some other unsavoury regime, how your supplies will arrive and all the other things that non-carrier countries have to worry about.
You want two carriers, and we British citizens and taxpayers want them too. We Want Two Or No Votes For You! ®
*Actually the Type 45 can't fight surface vessels at all, other than by firing unguided cannon shells at them (with little hope of results unless very lucky): but it could if it were a proper destroyer.
Lewis Page is a former Royal Navy officer, who left after 11 years' service in order to avoid wasting his time and the taxpayers' money aboard escort warships.