Do you think any official will undertake to demonstrate that possessing Trdient up to now has been good value for money? I don't mean vague hand-waving remarks about the deterrent effect for example, but real evidence that on such and such an occassion, country A behaved in a way that can only plausibly be attributed to the UK possessing a deterrent. There would also have to be convincing evidence that the fact that the UKs allies also possessed similar weapons would not have had the same effect.

Somehow, I doubt anyone will volunteer.