The second part of Chris Terrill's documentary about HMS Queen Elizabeth and last years WESTLANT 18 deployment is in BBC2 at 2000 GMT tonight. Last week focused a lot on the first F-35B landing and take off, but also mentioned the ASW role of the Merlin HM2.
I believe it is on BBC iPlayer too.
When the replacement for the Invincible class CVS (ASW carrier) was first studied in the nineties, it was apparent that larger carriers were needed. The 20 000 size of the Invincibles was a legacy of their origin as platforms for ASW in the NATO theatre, operating sufficient helicopters for constant dipping (sonar in water). It just so happened they making them just a little larger allowed a Harrier sized aircraft to be operated. This was useful as the Soviet submarines often carried missiles with guidance provided by Bears, so Harrier became Sea Harrier to 'hack the shad'. The addition of an AEW capability post Falklands meant that the jets could be used more effectively than standing constant CAP.
In the nineties, the small size of the CVS limited our ability to carry a meaningful number of jets, both Sea Harrier (primarily air defence) and Harrier GR7/9, plus the ASW and AEW helicopters. Post Cold War, the assumption was made that Cold War type missions such as ASW, fleet defence, protecting sea lines of communication and so on were things of the past, as we opted to fight campaigns in landlocked (or nearly landlocked), so the politicians, and public bought into the carriers = attack only type thinking.
F-35B was the only V/STOL successor to Sea Harrier/Harrier, and was intended to be capable of the full range of missions including Defensive Counter Air and Offensive Counter Air. Even without security and Geopolitical issues with Russia, it should have been clear that after Iraq and Afghanistan, the next conflict would most likely involve an adversary with naval and air capabilities such as submarines or MiGs.
Part of the problem (for the RN) is that no record was kept of why STOVL was the preferred option (cost of equipment, the training burden, manpower, and operating limits for smaller carriers in higher sea states) to inform the politicians, nor were the whole ship aspects of fixed wing flying properly articulated.