LONDON—There is one certainty in Brexit: London’s pre-eminent role in global finance has been diminished.

On Tuesday, the U.K. Parliament is scheduled to vote on a last-ditch effort to strike a deal on the country’s exit from the European Union. Talks were deadlocked Monday, but many politicians warned that Prime Minister Theresa May could face another humiliating defeat for her latest plan.

Some of London’s financiers have already voted, spending billions of dollars shifting staff and assets to outposts across Europe.

Regardless of how Brexit plays out, Europe’s financial system has been fundamentally altered, industry executives and analysts say. “Brexit forced a re-evaluation,” said Michael Mainelli, chairman of Z/Yen, a London think tank that ranks financial centers.

Hundreds of billions of dollars, as well as hundreds of finance roles, have moved to Europe’s secondary financial centers, especially Frankfurt, Paris and Dublin. JP Morgan Chase & Co., Bank of America Corp. and UBS Group AG are among those diversifying elsewhere.