No one has any evidence to what WILL definitely happen, just doom and gloomers who want nothing more than the UK to fail.
You're posting in a thread titled "$1 Trillian is leaving Britain" and claiming there's "no evidence anything bad will happen"?
Maybe take off your blinders and have a look around?
Financial Services tracker Ernst & Young found almost a quarter of financial services companies have confirmed a European relocation out of the UK by mid 2018
Is that not evidence, or do you think it's somehow good?