The days of Empire died a long time ago. We're just a small island off the coast of Europe. We shouldn't be wasting valuable money trying punch above our weight on the world stage. Our nuclear weapons program costs the tax payer billions. Personally, I'd rather see that money spent on the NHS, education, welfare and other areas of the economy.
We're the same Island we've always been. It's not as if it's shrunk since the days of old.
The world has changed and so has our part in it, that's clear. However it's still important (to me at least) that the UK maintains it's ability to project power across the world when needed. Whether it be to assist allies, to protect our interests or protect ourselves.
Nuclear capability plays a big part in this and is absolutely necessary to maintain the balance of power.