I think you need go and read up on passporting, and the impact an absence of passporting will have on London, and the foreign banks who use London as an entry point to European financial services.
When you have done that you will understand my reference to Frankfurt, the requirement for the American banks to be in Frankfurt (if London is not passported) and how the difficulties Deutsche and Commerzbank will make it even more critical they are there.
I've commented on passporting before. This was what the FT published regarding the view of the ratings agencies.....
Fitch Ratings has become the latest major rating agency to say UK-based banks and financial services firms can cope with losing their much-cherished ability to “passport” their services in the EU following the Brexit vote.
Should British banks lose their ability to operate across the continent with an EU-wide passport – a “worst case outcome” – the agency said it would not provoke any major change on lenders’ ratings.
“We believe the costs and disruption are likely to be manageable in the context of banks’ overall credit profiles,” said James Longsdon at Fitch.
The findings follow a similar verdict from rival agency Moody’s, which has called the loss of passporting rights as broadly “manageable” for the sector.
In the event the passport is lost, both agencies have touted the possibility of British banks using incoming European market rules, known as Mifid II, as easing the process of doing business on the continent following the UK’s exit.