On Wednesday, Theresa May will become Britain’s next prime minister. She'll become the second female British prime minister after Margaret Thatcher. Here's what you need to know her in 60 seconds. (Karla Adam,Jason Aldag/The Washington Post)

British Home Secretary Theresa May’s sudden ascension to her nation’s top job on Wednesday is likely to bring intense pressure to speed Britain’s departure from the European Union.

British leaders had planned to use the months-long process of picking a new leader of the Conservative Party to gain some breathing room before delivering the formal divorce notice, known as Article 50, to trigger the two-year negotiations over the split. 

But the surprise decision Monday by Energy Secretary Andrea Leadsom to bow out of the Tory leadership race threw the slow-walk approach into doubt.

A more protracted timetable could have given Britain a chance to come up with a negotiating position, which it still lacks in the absence of any planning for the withdrawal from the E.U. And some in Europe had hoped that the economic waves crashing over the British isles might persuade leaders there to abandon the divorce, or at least to find a way to preserve as close ties as possible. But with British Prime Minister David Cameron stepping down Wednesday, his successor will come under pressure from all sides to initiate the split.

Other European leaders want to minimize the uncertainty of British limbo on their economies. In Britain, some hard-line “leave” supporters also fear that a step-by-step move toward the E.U. exit could open room to challenge the decision.

“There should be no decision to invoke Article 50 until the British negotiating strategy is agreed and clear, which means Article 50 should not be invoked before the end of this year,” May said when she announced her candidacy for the leadership position shortly after last month’s referendum. That could prove to be a difficult position to maintain.

May was a reluctant campaigner for the “remain” camp, but she has repeatedly said that the country cannot ignore the referendum decision. “Brexit means Brexit,” she said Monday as Leadsom was folding her candidacy.

The prospect of a drawn-out British exit initially sparked fury from European leaders, who fear flatlined economies as businesses and investors wait to see the outcome of the split before making big decisions about where to put their money. 

As groups on the continent that are critical of the E.U.’s reach have been encouraged by the British vote, leaders in France and Germany, which both hold elections next year, want to deliver clear messages about the pain of a European pullout and the desirability of staying in.

German Finance Minister Wolfgang Schäuble pointed the finger at Britain last week, saying that the referendum “brought so much unrest to the E.U.” and that the rest of the bloc “must do everything possible to limit the damage.”

“Europe would be a laughingstock if, after such a decision, it were to say that you have as much time to think it over as you wish,” he added.

He said that market pressure could increase the longer the negotiations drag on.

If the timetable is indeed accelerated, the big winners could be those who advocate a more decisive split between Britain and the 27 other E.U. partners, analysts say.

Britain appears ill-prepared to conduct the complex trade negotiations with the European Union, in part because it ceded that function to the E.U. when it joined in 1973. The entire British government has just 20 active trade negotiators, compared with the E.U.’s army of more than 600 trade specialists, a former senior British Foreign Office official, Simon Fraser, said last month.

Once the two-year clock on the talks is triggered, those in the E.U. who want to drive a hard deal have time on their side.   After two years, Britain will be out of the E.U. even if no deal has been reached. Tariffs would be adjusted according to World Trade Organization rules, which could devastate Britain’s finance- and service-based economy.

In Britain and on the continent, those who advocated Britain remaining in the European Union had also hoped that the slower calendar might provide a window that would make clearer the economic pain of withdrawing. 

That could have fed support for tighter ties between Britain and the European Union, perhaps like Norway’s deal, where the non-E.U. member nation participates in the common market in exchange for following most E.U. rules.

“The more time you have to let the bad news sink in, the better chance you have to backpedal on this at least a bit,” said Jan Techau, the head of Carnegie Europe, the Brussels outpost of the D.C.-based think tank.

But Europe, too, could benefit from more time to arrive at a common position toward Britain, Techau said. Right now, countries are split between those that favor a fuller, more drastic breakup and those that believe a closer relationship could benefit both sides.

Ultimately, the shifting schedule may serve only to accelerate the inevitable: a painful severing of ties across the English Channel, one analyst said.

“Two months here or there is irrelevant. What matters is the substance,” said Charles Grant, the director of the Center for European Reform, a London-based policy organization that advocated staying in the European Union. “A lot of big businesses don’t realize how hard it’s going to be. We’re going to get screwed badly.”