A survey conducted by Innovate Finance of 100 member firms tapped into a deep well of dread about London's prospects as a European fintech hub in the wake of the referendum result.

"If the UK loses passporting and the seemless access to the European financial market that it has thus far enjoyed, both the finance and technology sectors will FLOOD out of London," says one survey participant. "The cost of living here is already way too high...as a cash strapped startup, trying to hire talent on bare-bones salaries, any excuse to leave to Berlin, Paris, Stockholm, Amsterdam, or Lisbon is one that we'd jump at."

Its worth noting here that the leading candidate to take over the leadership of the UK Conservative party, Theresa May, is refusing to offer any guarantees on the future rights of EU workers to remain in the country, further compounding the uncertainties.

Professor Peter Hahn of the London Institute of Banking and Finance, says the new world order is presenting Britain's financial services sector with a wholly unfamiliar set of new risk issues to ponder.

"The uncertainty of foreigners’ residency implies that every bank & finance business in the UK needs to quickly survey its employee register and understand the nationalities of its employees," he says. "Are some key people in the IT department German, Estonian, or Spanish? What about management? They may have been happy employees and they may be thinking about leaving. How replaceable are they?"

The UK's burgeoning fintech community currently employs 66,000 people, of which 30% are estimated to hail from the EU and overseas. The report cites money transfer firm Azimo, where three quarters of the workforce are non-Britons, as a typical example.

"Fintech human capital has complex skill sets, such as advanced computer science, regulatory understanding and knowledge of capital markets processes, and it is dependent on domain knowledge," states the report. "If UK financial services loses freedom of movement, we must ensure we can access the talent we need. Creating a more liberal regime for skilled workers (esp in tech) would be a potential angle here."

Other worries centre around a softening of VC inflows to the sector as uncertainty about the future drags on, a point which has been rammed home by the Bank of England in its recent financial stability report, which warns of a further deterioration of investor appetite for UK assets. The potential for regulatory fragmentation is also an issue, with firms concerned about access to EU-wide data sharing agreements emanating from a new crop of payments directives, and the application of anti-money laundering legislation and data protection rules.

Independent observers are no less gloomy. Dun & Bradstreest has moved to downgrade the UK’s risk rating from DB2a (on a par with the US) to DB2c, and anticipates that there may be further downward revisions in the coming weeks and months.

“Over the medium term, the most important question will be the nature of relations between the UK and the EU. Political developments, such as the outcome of the Conservative Party leadership contest and when Article 50 is invoked, will severely impact the economy," says the ratings agency. "Against this backdrop of elevated uncertainty, investment activity will remain subdued and the UK faces a period of lower growth. In the worst case scenario that the UK loses access to the common market, there would be very negative repercussions for the wider economy, with the financial sector being hit particularly hard.”