HSBC are moving Euro transactions out of London if the UK leaves the single market.
http://www.bbc.co.uk/news/business-36629745
Expect a similar statement from all of the major banks. The reasons why this has to happen are technical, not economic.
My daughters partner works there, he thought they might end-up moving to the far East, but it looks as if it might be a bit nearer - I'll have to brush-up my French.
I always thought this might a significant portent coming as it did just before the referendum:
http://www.bbc.co.uk/news/business-35818997The Germans were worried that it might mean the Deutsche Boerse might effectively be moved to London, now it looks like it could be the opposite!