A measure of the strangeness of the times in Brexit Britain is that one can buy T-shirts bearing the face of John Bercow, the speaker of the House of Commons, in the stylized stencil preferred by street artists and skateboarders, with the word ORDER.
“He is spitting the best sassy statements in that charming accent,” said Kaarlo Junkkari, a 19-year-old Finnish man who sells the T-shirts online. He said he had become fascinated with Mr. Bercow, whose prolix verbal style and braying cries of “order, order!” have made him one of Brexit’s “spicy memes.”
But this enthusiasm is not universal in Britain, especially on Tuesday, after Mr. Bercow startled the country by blocking Mrs. May’s plan to push her withdrawal agreement through Parliament before a trip on Thursday to Brussels. He announced that he would not allow a third vote on her plan for Brexit, as the departure from the European Union is known, unless the plan differed from the one rejected last week.
This ruling — based on an obscure precedent from 1604 — has made Mr. Bercow, a wonky arbiter of parliamentary procedure, one of the most admired and hated men in the country.
Pro-Brexit newspapers branded him the “Brexit Destroyer,” a “pompous, preening, puffed-up figure” who had “sent a wrecking ball crashing into the most important political process in decades.” A BBC camera crew trotted after him on his morning coffee run on Tuesday, peppering him with questions about what he meant to do next on Brexit.
“I certainly think he sees this as his big moment, that this is what he will be remembered for,” said Bobby Friedman, the author of a biography of Mr. Bercow. “He’s probably more powerful in the Brexit process than Jeremy Corbyn is. Corbyn is being pushed by events, whereas Bercow is pushing events. He is in control of it.”
The 56-year-old son of a Jewish cabdriver from North London, Mr. Bercow rose through the ranks of the Tory party through sheer elbow grease, and then resigned from the party when he took the nonpartisan role of speaker, in 2009.
He inspires a visceral loathing in many of his former Conservative colleagues, in part because his politics shifted to the left late in life. He brought a new aggression to the role of speaker, cutting off lawmakers with comically fusty insults if they spoke too long. Simon Burns, the health minister, was caught on microphone in 2010 calling him “a stupid, sanctimonious dwarf.” (Mr. Bercow is 5 foot 6 1/2 inches.)
But never, until Brexit, was he accused of trying to block the government’s critical legislation.
Commentators on Tuesday picked apart Mr. Bercow’s decision to bar a third vote on the withdrawal agreement, on the basis of a line on page 397 of Erskine May’s 1844 guide to parliamentary procedure, last invoked in 1920. Critics said Mr. Bercow has taken an anti-Brexit position from the beginning, marshaling parliamentary procedure selectively to frustrate it at every turn.
“Trust and faith in his impartiality has broken down,” said Stephen Laws, who formerly drafted legislation for Parliament, and is now a senior fellow at Policy Exchange, a research organization in London.
Mr. Bercow suggested on Monday that he might go further if Britain heads toward a no-deal Brexit, by allowing a parliamentary vote to revoke its departure from the European Union, using an emergency measure known as Standing Order 24.
“Given that he decides what his own powers are,” Mr. Friedman said, “it is within his power to do so.”
But some legal scholars defended Mr. Bercow’s decision making, saying it is in line with his longstanding advocacy of the right of Parliament to challenge the executive branch. The Brexit process has been tightly and secretively controlled by Mrs. May, and lawmakers have struggled to find any way to influence the policy, said Jack Simson Caird, a former legal adviser in the House of Commons.
Her efforts to steamroller her plan through Parliament by forcing repeated votes on the same legislation, he said, have roused Mr. Bercow to action.
“People are right that he’s taking a stand,” he said. “He has always been engaged in a system of checks and balances. It’s not in the Commons interest to be made to look ridiculous. He’s trying to defend against that, and I think that’s legitimate.”
For his part, Mr. Bercow said in a recent interview that he would not be “intimidated by some moaning minister in any government,” and that his guiding principle was to stand up for the parliamentary underdog.
“It’s not for the speaker, let’s say in the context of Brexit, to prescribe one route or another, and I think the record will show that I’ve always been keen to give support to the minority, or dissident voices in the House of Commons,” he told CNN. “I think the speaker’s role is sometimes to stand up for the institution of the House of Commons.”
And some analysts, on Tuesday, said his intervention amounted to a necessary check on power.
“The constitution has worked, despite the theatrics,” wrote David Allen Green, a legal commentator and contributing editor at The Financial Times. He noted the remark of Robert Buckland, the solicitor general, that Britain was in the midst of a “major constitutional crisis.”
“His complaint is itself the sound of a working constitution,” he wrote. “Had the executive succeeded in its intended power grab, that would have been a constitutional crisis. But, so far, that has been avoided.”