@KYli bro let them do it, it will spell the end of London as one of world financial center. I hope @Gatekeeper can add more, but with Brexit they need more friends and investment than ever before, with them leaving EU, they're relying on the US as their savior instead the American throw them under the bus. Such condescending attitude need to suffer a bloody nose to understand its present situation.
My solution for UK , with brexit they need to play all players instead of relying on its traditional allies, Britain is far away from Russia and even more from China so both are not a threat. They wanted to play in the big league which with their current status is laughable. The hubris need to be crush for them to able to move forward. And among its allies (EU) they 're trying to set an example out of UK the consequences of leaving the EU project.