Point being
1. The D5 DOESN’T work fine…in Royal Navy hands.
2. Having only one boomer capable of going to sea at a time means you are only one single point failure - be it engineering catastrophe, navigational error, or enemy action - away from not having an underwater nuclear deterrence at all. Built in the 1990s with a designed lifetime of 25 years and the Dreadnought follow on boats delayed at least ten years, their maintenance problems can only get worse.

https://ukdefencejournal.org.uk/the-...arine-patrols/

The only really satisfactory solution is to replace these four aging boats with the Dreadnought class. But the first boat of that program (which was started in 2016) is not expected to be operational before late 2032 assuming no glitches and actually getting currently projected funding levels so the existing boats are going to have to at least share the load pending commissioning of the fourth and final Dreadnought series “in the 2040s”.
3. And no, you can’t depend on an operator to assure your cities survive, but when you are using an INTERCONTINENTAL BALLISTIC MISSILE to hit an adversary it would be nice to have said missile hit closer to the adversary than your own boat. A CEP of half of the globe is a little too big even for a nuke.
https://nationalinterest.org/blog/bu...ared-ps-030826

4.. The lesson learned from the last two launch attempts is that the personnel involved were less competent than their predecessors. That’s not a real comforting lesson.