LONDON ― It should be a dream Brexit scenario for the City of London: a chance to break away from the EU and move closer to the U.S.

The square mile has been offered the opportunity to modernize with New York and immediately reap the benefits of a faster-moving financial system, rather than wait around for the slow-churning bureaucracy of the EU.

But, as has proved the case several times in the recent past, the City seems reluctant to take advantage of this particular potential Brexit dividend. Its denizens would rather stick with the EU, even if the whole point of leaving the bloc was to be able to go it alone on financial rules.

It fears potential for disruption without the EU on board, given the amount of business that still function across borders.

This time, the qualms center around the technical issue of securities settlement — or how quickly shares are exchanged for cash.

The U.S. will move from a two-day to a one-day cycle by May, in a bid to make markets safer by freeing up cash and reducing the risk that the other side of the trade goes bust.

But the American plan has created a Brexit flashpoint between the U.K. and EU, where a two-day window is still the norm, because Britain has the means to move faster without 27 other countries in tow.

And a government-backed report, published Thursday, said the U.K. should be willing to go ahead on its own if the EU is not ready by the end of 2027.

“There is a clear consensus that the U.K. needs to move. There’s a clear consensus it’s about a two-year project,” said Charlie Geffen, an industry veteran who chaired the report.

Geffen, a senior adviser at the consultancy Flint Global, backed working with the EU on timing in his report, but only to a point.

“If that cannot be achieved within a suitable timescale the U.K. should proceed in any event,” the report said.

The U.K. government has already accepted all of Geffen's recommendations. If it wants to, it can plow ahead with the timing change earlier — with the potential to label it as a "Brexit benefit" which would not have been possible had the U.K. not left the EU.

Not without EU

But the City just doesn’t want to go it alone.

The Association for Financial Markets in Europe, which represents the biggest investment banks, said the two sides should “adopt a collaborative approach in order to reach a pan-European consensus on timing.”

And the Investment Association, a forum for U.K. money managers, said “alignment across global settlement cycles is the most optimal outcome.”

“We encourage the close collaboration of U.K. and European authorities on this matter,” said Alex Chow, investment operations policy lead at the trade body.

It's not the first time the City hasn't wanted to break free after Brexit — after all, many of the banks, insurers and money managers set up in London still use it as their main European base.

Still, it'll ultimately be a political choice for Britain to hold off as it's likely to be ready sooner, while the EU will need longer to make the change because it has more fragmented financial markets. And EU officials say Brussels wants alignment with the U.K.

Mairead McGuinness, the EU’s commissioner for financial services, made clear earlier this year that it’s a question of when, not if, the EU speeds thing up.

Verena Ross, head of the bloc’s financial watchdog, urged EU players to start preparing for a switch even as her organization consults on its plans.

The Geffen report effectively sets a deadline for the EU of the end of 2027 — after which too much dithering may try Britain's patience.

The 2027 timeframe in theory should be enough time for the bloc to propose legislation, as well as giving EU industry time to change their operations.  

And until then, the U.K. looks willing to wait.