Timmyhawk

As explained below we cannot reverse nuclear arms already aquired in the countries that have them. So, a realistic policy should firstly work at reducing their numbers, an area in which Britain is leading by example. The next realistic step is to stop further proliferation. The risk of this exists in two broad regions: the Pacific and the broader Mediterranean and greater Middle East.
Let's get the Pacific out of the way, as this is outside Britain's strategic sphere. The consequences of North Korea getting away with its programme and a possible weakening of American leadership could lead to the following chain reaction of nuclear weapons aquirement: South Korea & Japan, Taiwan, Australia and Indonesia.

Looking into our own region, let's have a look at the consequences of a nuclear-armed Iran, coupled with a possible drawdown of US-UK regional military policies: Iraq, Saudi Arabia and Turkey as the first in line would go nuclear first. In turn this would pressure and open opportunities for Egypt, Lybia and Greece. Leading on from there Algeria and Syria can also not be discounted entirely. Once this is getting underway, who can say that other European powers, especially Germany will not be tempted as well? Additionally remember the strategic pressure represented by Russia.
This is bad for Britain's security. So, in order to counter this we will have to work on strategic arrangements and security deals that will lift the potential burden of Iranian/Russian nuclear blackmail from these countries. This would require resetting our alliances and making it clear that armed conflict will at some point draw in British military force, which must, and will, ultimately be insured with nuclear weapons.
Such a policy would not be able to reverse nuclear weapons in any of the countries in our strategic neighbourhood (Britain, France, Israel, US, Russia, Iran), but it would prevent the spread of such weapons to other countries.

(See also this article in the JPost by Emanuel Adler on the Israeli case, which makes a good point, similar to mine, and which ties in with this earlier posting).

TRIDENT RENEWAL: TOWARDS NUCLEAR DISARMAMENT
Needless to say, it would be nice to be done entirely with such expensive and dangerous weapons, but Britain alone cannot not achieve anything with unilateral moves, except disadvantage the UK’s strategic position.
However, nuclear disarmament can only work if all potential competitors agree to do likewise, and in a simultaneous and verifiable fashion.

Who would that be for Britain/France/EU? And what other factors might drive their nuclear programmes?
Iran: Strategically this is a fairly direct neighbour. Iran claims in addition to us and the French, the US and Israel as concerns. Rivalry of course also with Russia.
Russia: Whilst there may not be much threat of any kind of serious conflict, we cannot know what the future holds, and in addition growing energy dependence on Russia would mean that our nuclear climbdown would shift the balance of power and influence excessively to Russia. So, what drives Russian nuclear arms policy? Its additional strategic neighbours and competitors are Iran, China and the US.

What follows from this? These countries would now have to be considered in a disarmament deal. So, like above:
Israel: To offset its numerical and spatial disadvantage vis a vis its neighbours, and because of Iran's programme, any Israeli disarmament moves are effectively impossible. And who knows who will follow in the region once Iran goes nuclear and the US-UK coalition abandons the region to its own devices: Iraq, Turkey, Saudi Arabia and Egypt are the most likely candidates; but more on this later.
China: Obviously the US is the main concern for China and additionally India plays a role, just as North Korea will be of some concern. Additionally a failure to contain North Korea and the weakening of American leadership would lead to more proliferation: most likely Japan, South Korea, Taiwan and maybe Australia.
US: Strategic concerns about Iran, Russia, China and North Korea.

So again: What follows from this? These countries would now have to be considered in a disarmament deal. So, like above:
North Korea: nukes used to extract international aid, strategic concern about the US and China.
India: Rivalry with Pakistan and China.

If we now add in Pakistan (vis a vis India, perhaps Iran), we have all the world's nuclear powers involved. From this we can conclude that the nuclear disarmament of Western Europe will only be possible within a framework that sees total global nuclear disarmament.
Whilst the likelihood of this is fairly small, formulating this as an end goal for British foreign policy to support is nonetheless right.
But before this can come about, Britain is right to keep its nukes, while making sure that the numbers are as small as possible. And on this, the Government for once seems to have got it right.