UN Preventative Nuclear Capability

A few people in the United Kingdom are deciding (or have decided) whether or not to renew our nuclear capability (since our old nuclear missiles are to pass their 'best before date' at some point in the future.)

The thing is, the UK doesn't really need nuclear weapons. For the forseeable future, the only people who could ever conceiveably 'nuke' us are crackpot dictators (or terrorists). If we were to be thus attacked, it doesn't really seem very nice for us to bomb the unfortunate citizens likely suffering under the given dictator. However, it the logic runs that the existence of our own nukes will deter said dictator from the initial attack.

So, to the idea: Rather than the vast expense to, and international imbalance of, a few nations having a nuclear force, I propose that the United Nations commissions its own nuclear force*, which is to be made AUTOMATICALLY available as appropriate to any nation that is bombed (with a nuclear weapon), so that a retaliation can take place. That the UN holds this capability means that even a completely obliterated nation could make a sizeable response. Of course, it is to be hoped that such will never have to be used. But it means that every nation has the fortune and security of a nuclear deterrent. It is then to be hoped that the attraction of acquiring nuclear weapons would be much decreased, and ultimately one might hope that only the UN would possess nuclear weapons, which could then be gradually scaled down. Armageddon avoided in time for lunch..

*Or the US and others donate some of their own sizeable arsenals.

Footnote: Developing a nuclear capability can also be argued to provide a nation with i)diplomatic clout and ii)increased economic activity. I would suggest that the first is just unfair, and the loss of the second a small price to pay. Apologies if this idea has had a previous airing.