Opinion | Will the U.K. Ever Get Closure on Brexit?

“Super Saturday” was to have been the decisive moment for Brexit, the first Parliament session to be held on a Saturday since the Falklands War. Members of Parliament were to cast a “meaningful vote” on the surprise deal Prime Minister Boris Johnson brought back from Brussels last week. Proponents of Brexit sensed closure, while opponents took to the streets outside Westminster by the hundreds of thousands to demand a new referendum.

After hours of raucous debate, the speaker of the House of Commons, John Bercow, announced that the votes were in — for another delay. As with so many earlier “pivotal” moments gone awry in the convoluted saga of Britain’s attempt to quit the European Union, this one only introduced a new array of unknowns.

Under earlier legislation adopted by Parliament to prevent a no-deal Brexit, the vote compelled Mr. Johnson to ask the European Union for another extension of the deadline for the divorce, which is now Oct. 31 — something he has said he’d rather be “dead in a ditch” than do. He made his reluctance abundantly clear by attaching the formal request for a prolongation to a letter urging the bloc not to grant his request.

But then the entire Brexit deal that Mr. Johnson unexpectedly brought back on Thursday was largely the same as the one he had strenuously opposed as a leading Brexit hawk when his hapless predecessor, Theresa May, tried to pass it through Parliament. The major difference was a new solution to the vexing problem of maintaining an open border between Ireland and the British province of Northern Ireland once Britain dropped out of the European Union’s joint market. Mr. Johnson’s solution was essentially to install customs controls at the Northern Ireland border. The loyal Mrs. May strongly endorsed Mr. Johnson’s version.

In the end it was not opposition to Mr. Johnson’s deal that blocked it, but lack of trust in Mr. Johnson. Upon taking office, the grandiloquent prime minister had attempted several end-runs around Parliament in the evident hope of getting to the Oct. 31 deadline without a deal, an outcome most responsible officials and experts — but not Mr. Johnson and his coterie of “hard Brexiteers” — deem disastrous. Many members of Parliament feared that if his deal was passed, he and his allies would tie up enabling legislation until the deadline ran out.

So Parliament took up an amendment proposed by a former Conservative Party member to postpone voting on the agreement until the rest of the legislation was passed. It won 322 to 306, and an irate Mr. Johnson yanked his bill, evidently intent on reintroducing it in the coming week. Intensive vote-counting over the weekend suggested that Mr. Johnson’s deal stood a decent chance of eventual passage.

That would ensure an orderly divorce with the European Union — but not the end of the process. There would remain months of detailed negotiations on the mechanisms and details of disentangling four decades of association, most likely to be preceded by another national election. The massive demonstrations outside Parliament on Saturday made clear that every step of the way would be bitterly contested.

In the three years since the British voted by a narrow margin to quit the bloc, the debate has gone far beyond the simplistic promises of Brexiteers like Mr. Johnson, who painted a rosy and unrealistic picture of Britain reviving its past glories and saving dollops of money outside the Union. Yet greater awareness of the true complexity and cost of Brexit has not dimmed the passion of those who despise the very idea of sharing sovereignty with the Continent.

What has been consistently clear to a majority in Parliament and to the European Union is that an exit without a deal cannot be allowed. However raucous and impassioned the debates, the Parliament has rebuffed any efforts by Mrs. May or Mr. Johnson to short-circuit democratic process, as it did again on Saturday. The decision on Brexit will affect Britain for generations, and all the delays and debates, however acutely frustrating, are better than a rushed or questionable exit.

It may be that the moment has come, and Mr. Johnson will get his deal through Parliament this week. Or not. Either way, decisions taken in the coming days must not be a surrender to “Brexit fatigue” on either side. Too much is at stake, and too much more lies ahead.