[user104658]

Here's the sitch: there are only two vaguely realistic situations in which the UK will be hit by a nuclear attack.

1) An attack by an extremist organisation like ISIS that has somehow got their hands on a small nuke.

2) The superpowers kick off.


These are the ONLY realistic scenarios and in BOTH scenarios a nuclear deterrent is about as useful as an army of cats armed with potato guns.

In scenario one, the attackers are a decentralised organisation operating from cells. Even in the countries where they have greater numbers, there is simply no target to nuke. They are not a nation, they are a swarm, they don't care if you fire nukes back. It's like trying to take out a swarm of bees with an assault rifle.

Scenario two, we are all completely and utterly ****ed and there is nothing left to defend. In fact holding nukes only make us more likely to be a target when the first bombs drop. Which might actually be better than the radiation sickness and aggressive cancers that will get you otherwise, I guess.