Good enough for Ivan back then, good enough for him in the future.
Strategic Deterrent required to counter real nuclear weapons states.
Sub Strategic (or missile defence/BMD) required to counter the collection of loons most people currently think of as "the threat".
Easiest way to cover both is SSBN plus D5 Trident SLEP with pointy-end variations.
Anybody under the misapprehension that Ivan is going to be our buddy forever more needs to consider what a booming economy (coupled with a proven ability to make dangerous kit) might mean twenty years hence.....
The deterrent is insurance. In this case the difference is that you can't just ring up Zurich or Directline and get covered in a matter of minutes.
WEBF and GBZ are entirely correct, the deterrent is a national not naval issue and should not be a question of either / or CVF.