Leviathan was the only Majestic left in the UK. She was not scrapped until 1968.
Depending on the timeframe, up to 1962 at least I counted six hulls still around. Although Leviathan makes the prime candidate, of course.
First the age of the ships.
With the eventual longevity of both Hercules/Vikrant and Hermes/Viraat I have certain doubts about this argument. I already noted it elsewhere, but looking at repairs schedule Hermes didn't start to show critical age problems till around 2006, and tropics aren't easier on ship's metal and structure than the Atlantic. I think RN underestimated the hull life potential in many cases, for political or other reasons.
- Second new ships are more cost effective.
- Third the RN had been stung too may times by rebuilds/completing suspended ships to new designs going over time and over cost by the POD.
On the other hand, there is this persistent political fiction that rebuilding is not as painful for the parliament to swallow as building a new unit. Add to it a cancellation of redundant program or two, and it may just pass even before the 1966 review.
However, that's the only way I can see it happening.
This does deserve a separate overview.
Generally, I like those conversion programs very much. Although for some reason all of them have double ended missile launchers and totally sacrifice the aerial capabilities, but it could be suggested that for ASW operations the launcher is placed only forward (with angled deck) or only aft (with cut deck) we can get more or less the same result as
@Dilandu suggests above, initially for helicopters only, but with inevitable addition of Harriers a decade later. And considering the speed of missile development the modernization program will be signed off in early 50's and already paid for, but the ships won't be ready before Sea Slug does, i.e. around 1960.
It could work, actually.
There would be a headache to replace the Sea Slug with Sea Dart if ever this would be contemplated, or during the 70's the missile launchers would be removed to increase back the deck and the hangar for Harriers. They will still need newer sonars and electronics.