Old joke - what are you doing ? Sprinkling woofle dust. Why are you sprinkling woofle dust ? To keep the elephants away of course ! But there aren't any elephants in Clacton. Just goes to show it works.
Trident is much the same, it has deterred attacks on the UK in much the same way no one has nuked Peru, i.e. not at all.
The Government has published a review on possible options to replace the Trident Nuclear Missile System with a slightly less expensive alternative. The Conservatives have already denounced the option as a part-time deterrent.
Trident is inherently useless. Lets save the money and spend it on something else. My favourite is more overseas aid. Funny how people you are helpful too are less likely to go to war with you.