Close scrutiny of UK financial firms’ European Union outposts will continue indefinitely, the bloc’s securities watchdog said, as regulators begin a round of new checks on how they are operating.

Trading in euro-denominated swaps has fallen sharply in London since Brexit, with volumes moving to New York, Amsterdam and Paris, financial data company IHS Markit said on Thursday.

Pan-European exchange Euronext said on Monday it will clear all trades on its newly acquired Italian platform by 2024, helping the European Union cut its reliance on the London Stock Exchange for core financial activities after Brexit.

Goldman Sachs Group Inc. is shifting some of its euro swaps trading desk to Milan from London, the latest example of roles moving to the continent after Brexit.

All the talk was of Frankfurt or Paris luring London's financial business as Britain peeled away from the EU. Yet it is Amsterdam that is proving the most visible early winner.

One of the biggest Brexit battlegrounds between the European Union and the U.K. now has a price tag: at least $2.4 million a day.

Trading in euro-denominated swaps has dropped by nearly 30 per cent in London since the end of the Brexit transition period on 31 December, with trade primarily shifting to New York, Amsterdam and Paris.

New York has increased its market share in trading euro interest rate swaps at London’s expense, data group OSTTRA said on Thursday, in the latest sign of how global financial markets are being permanently fragmented by Brexit.

The City of London lost 2.3 trillion pounds ($3.3 trillion) of its lucrative derivatives trading business in March alone, with Wall Street trading platforms gaining the most from Brexit.

The City of London’s chief coping mechanism for dealing with Brexit’s threat to the financial services business is to dismiss the loss of jobs and investment as a trickle rather than a flood.