The tune "Rule Britannia" was the marching song for the 'patriots' who pushed for an independent UK based policy.
The result was the industrial revolution and the UK becoming the pre-eminent power on Earth.
So we've sort of done this before.
No it wasn't. This has never happened.
It's really hard to conclude that anything so tangentially related and which happened such a long time ago could possibly be relevant.
The biggest problem seems to be lack of acknowledgement of the UK role in the world, at best dwindled ever since they lost both WW, the only colonial territory worth mentioning (i.e. India) and recently becoming CHAV land. The rest of the involved parties (such as Germany and France, but also including the most of western Europe) took notice of how the world was, and did their best to ensure their position in the coming years. To some remarkable success I must say, the EU (even when discounting the 28th member) is still the biggest economic zone in the world, and after the final departure of the UK it will certainly develop a tighter union including a common military, new federal institutions and so on.
All of which seems to escape the 'Rule Britannia' crowd such as you. Congratulations on your Darwin price! Maybe is time for you to read up on some science ...