Britain’s Parliament, with a statue of Winston Churchill in the foreground, voted Feb. 1 on a plan to leave the European Union. (Andy Rain/European Pressphoto Agency)

Britain’s House of Commons voted decisively Wednesday to authorize Prime Minister Theresa May to trigger the start of the country’s exit from the European Union.

The outcome of the vote was never in doubt, even as lawmakers spent a second consecutive day arguing the merits of a departure that the bitterly divided country approved in a June referendum.

The margin of Wednesday evening’s roll call, 498 to 114, gives May a convincing mandate as she prepares to launch divorce talks with the E.U. by the end of next month. Once that is done, Britain will have two years to negotiate the terms of its departure.

Wednesday’s vote was necessitated by a British Supreme Court ruling last week that Parliament, not the prime minister, should have the final say on whether Britain leaves the E.U.

May’s government had vigorously contested that notion, pursuing appeals in a bid to keep the departure, known as Brexit, from becoming entangled in parliamentary debate.

Protestors demonstrate against Brexit in Parliament Square in London. (Leon Neal/Getty Images)

Her reluctance stemmed from simple arithmetic: Although the British public voted 52 percent to 48 percent to quit the E.U., most members of Parliament had favored staying in.

[Should Britain host Trump for a state visit? More than 1 million say no.]

Even so, many pro-remain lawmakers calculated that the political cost of blocking Brexit would be high, and they chose to align themselves with the public’s will.

May had the resounding support of her ruling Conservative Party, which has been divided over Britain’s E.U. membership for decades. She also won backing from opposition leader Jeremy Corbyn and his Labour Party, though a significant number of Labour members bucked their leadership by voting no on Wednesday.

“Those of us who campaigned for remain know that Brexit is to happen,” said Stella Creasy, a lawmaker who was among the Labour rebels. Voting no, she said, was “the only chance to send the prime minister back to the drawing board.”

The Scottish National Party — the third-largest in the House of Commons — and the Liberal Democrats also lined up against Wednesday’s legislation. But they came nowhere near stopping the bill, and amendment proposals intended to influence May’s position in the exit talks also fell short.

The bill was written as simply as possible to minimize debate and maximize May’s latitude for negotiation. In a mere two clauses, it gives May permission to trigger Article 50, the never-before-used mechanism for leaving the E.U.

[Transcript: Theresa May’s speech on Brexit]

The public “voted leave because they wanted to leave,” said Conservative lawmaker David Warburton, urging his colleagues to back the vote.

The bill still needs approval from the upper chamber of Britain’s Parliament, the House of Lords, but that is considered a formality.

Despite the lack of suspense in Wednesday’s vote, lawmakers staged a passionate debate over some 16 hours, with more than 150 members weighing in.

May has signaled she intends to push for a clean break from the E.U., with Britain leaving behind the common European market for goods and services as well as the customs union that regulates members’ trade within and outside the bloc.

The prime minister has insisted that Britain intends to transform its ties to Europe, not sever them. But European leaders have taken a hard line, saying that Britain will not be able to cherry-pick the best parts of E.U. membership while shunning the responsibilities.

May has also annoyed European allies by seeming to cozy up to President Trump. While other European leaders took a cautious approach to a leader seen by many on the continent as erratic and politically toxic, May flew to Washington within a week of Trump’s inauguration and proclaimed her desire to strike a trade deal with the new administration.

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