Jacko,
I'm not trying to justify the independant nuclear deterrent (nor am I or was I a matelot)
You are correct in stating that there is a lot of cold war thinking in nuclear deterrence strategy; that's were the IND, and our current policy evolved from.
I'm merely pointing out some elements of deterrence theory (as formed by far greater minds than mine) and the reality of the nuclear non-proliferation treaty.
There is no evidence that advanced democracies would act in any specified way towards any change in posture by the 5 nuclear powers (which, by the way is the NPT legal status of the UK, China, Russia France and the US, irresprective of who owns nuclear weapons).
There is however, plenty of evidence that many countries observe the NPT with great reluctance because it a treaty which discriminates in favour of the five NWS. India would not sign it and developed nuclear weapons, impervious to the will of the world, as did Israel. India's weapons prompted Pakistan to go nuclear, and Israel's weapons are a major driving force for an Arab nuke one day.
Whether you like it or not, our IND exists to help maintain the nuclear status quo. Downsizing it would be destablilising as it would be identified for what it would be - the backbone of a low cost, high deterrence military strategy. Great for us, but a complete abuse of our status within the NPT. If it seems complex that's just because it is. Already analysts and Government advisors have noted that as nuclear weapons diminish (which they are obliged to do under the NPT) the relative cost of ownership diminishes and therefore the attraction of ownership increases. The end game is not clear: can we get rid of all nuclear wepons safely, or will attempting to do so unleash a sudden charge for ownership amongst those with the technology in place?
In this context many people would argue that getting rid of all our nukes is not only the most cost effective option, it is also one of the safest. Equally, many more (including our mainstream political parties) think now is not the time to give it up.
On a personal note (as all I have written is really just plagiarised from deterrence theory) I an not optimistic about the long term outcome whatever the UK chooses to do. I've always thought the genie has long since escaped the bottle and it is only a matter of time before a nutter gets the bomb and/or somebody somewhere chucks a few about.
Still, I live in Scotland and when the SNP get in they are going to get rid of the UK's IND anyway, so at least I'll be in nuclear free state.