For Leon - Tube-launched TLAM (as can be used by UK SSN) is highly likely to be out of service by the mid to late 20s - unless we pay to retain that capability. Plus (as ever) you risk nuclear alerts every time you want to give someone the good news with a conventional one.
On the paper :
Apparently a single RAF squadron is going to be able to hold sufficient targets at risk by delivering 30 weapons. At 2 buckets per Dave, that means a 15 ship successful penetration, so if you factor in attrition from a half decent Russian IADS, that's a lot of cabs launched - and more to the point, a lot of tankers we ain't got. Doesn't smell like a single RAF squadron to me - or a second RN squadron for that matter. Particularly not if launching from UK and proceeding at a sedate 450kts or thereabouts. 3-4 hour run to get to St Petersburg?
All of it rests on this rather ethereal idea that the Moscow criterion is no longer valid. Given that nice Mr Putin seems to be a bit short on manners atm, I'd personally want him to be sure we'd be able to entomb him if we had to, rather than just incinerate several million Russian civpop.
There's also the rather quaint idea that we'd be able to defend our "dispersed" force from attack. There's a limited amount of dispersal options which would be known to opfor. It doesn't take a genius to go after a large part of that subset (by a number of means) which immediately reduces your oppos defensive problem. They're almost inviting an attack on the UK, something you don't really get with CASD.
That's before you get to the warhead design issues, additional force structure etc etc.
I'm afraid it all smacks of "I don't like Trident and I want to find a way of presenting binning it as a cut to the deficit without pain in social spending or tax rises. How can we get it cancelled without looking like unilateralists and promise more defence while achieving savings (which we may or more likely may not actually put towards defence)?"