Some of the biggest names in the City were out in force on Thursday demanding a Brexit deal that maintains free trade between London's financial sector and the rest of Europe, and allows the market to determine where trillions of pounds worth of daily transactions are cleared.
Their comments jarred with a warning from EU chief negotiator Michel Barnier who said the UK could not expect "frictionless" trade post-Brexit.
"A trading relationship with a country that does not belong to the European Union obviously involves friction," Barnier said earlier in the day, insisting the UK's decision to leave "had consequences" for business.
Yet UK financial watchdog chief Andrew Bailey warned Brussels not to use Brexit as an excuse to restrict "freedom of location".
Bailey, who heads the Financial Conduct Authority, said: "When I hear people say that firms need to relocate in order to continue to benefit from access to EU financial markets, I start to seriously wonder: Does Brexit have to mean abandoning the benefits of free trade and open markets in financial services? It should not."
He added: “There is ample evidence that open markets in financial services and free trade can exist safely without common detailed rules and shared regulatory institutions. Consistent outcomes of regulation are what matters.”
Bailey was referring to attempts by some EU politicians to seize London's prized euro clearing market.
Barclay's chairman John McFarlane, City of London Corporation policy chief Catherine McGuinness, and London Stock Exchange chief Xavier Rolet also weighed in, attacking moves to break up the City's clearing business.
Speaking at TheCityUK's annual conference, McFarlane said "fragmenting [London's] superior offering" in derivatives trading would lead to higher costs for businesses, and that the City must apply the "strongest political pressure" it can muster to ensure clearing was at the top of the political agenda.
McGuinness struck a similar note, warning that "cherry-picking clearing and other services" would be a huge risk for the EU, which benefits from London's comprehensive offering in financial services.
Meanwhile Rolet predicted "more integrated financial regulation" across borders, and urged the EU to keep an open approach to trade in financial services.
Elsewhere on Thursday, trade secretary Liam Fox travelled to Paris to promote "the freest possible trade between Britain and the European Union".
And Carolyn Fairbairn, director-general of the Confederation of British Industry, used a speech at the London School of Economics to stress the importance of transitional arrangements, arguing that the prospect of a cliff edge scenario "is already casting a long shadow over business decisions."