In nearly a millennium of history, the Palace of Westminster has played host to kings and queens, endured Nazi bombing raids and showed the world how a people could govern themselves through representative democracy.

But it has never seen a day quite like the one expected on Monday, when the building's cold stone walls will echo with a parliamentary debate over whether to ban from Britain the leading Republican contender for president of the United States.

It will be a strange moment for politics on both sides of the Atlantic. Normally, British officials avoid getting involved in U.S. politics - and vice versa. The Anglo-American alliance, a bedrock of Western security, is supposed to transcend politics.

Donald Trump's reality-show-style emergence as Republican front-runner, however, is putting that notion to the test.

Brits have watched his rise with a mixture of bemusement, alarm and indignation - the latter coming after he alleged that certain areas of London were off-limits to police because of rampant Islamic radicalization.

The parliamentary debate was triggered when more than a half-million people signed an online petition arguing that Trump should be outlawed from visiting Britain because of his call last month to ban Muslims from entering the United States. Trump's proposal, petitioners said, amounted to "hate speech."

For three hours on Monday, members of Parliament will have a chance to say whether they agree. But while Trump's words have been widely condemned in Britain - from all sides of the political spectrum - there is little chance he will be banned. Instead, he may well find himself invited for a visit.

"I'd offer myself as a guide to take him around town," said Paul Flynn, a member of Parliament from the center-left Labour Party. "I'd be delighted if he took me up on it."

Flynn has been designated to argue on behalf of the petitioners who want Trump banned - and Flynn said in an interview he has sympathy for their cause. Trump's remarks on Muslims, Mexicans, women and the disabled, Flynn said, "are outrageous."

But Flynn said he will ultimately argue against a ban.

"The last thing we want to do is assist him by awarding him a garland of victimhood," said the 80-year-old, who represents an immigrant-heavy area of Wales. "A ban is not going to achieve anything. It would be far better to test his claims."

The Muslim Council of Britain has taken a similar line, calling for Trump to name the no-go neighborhoods of London and saying it would be happy to "organize a multi-faith delegation to accompany Mr. Trump and tour these areas." The group even promised to pay for Trump's lunch.

The British Home Office, which has the power to ban Trump, said in response to the petition that "coming to the U.K. is a privilege and not a right and [the Home Secretary] will continue to use the powers available to prevent from entering the U.K. those who seek to harm our society."

But the statement also said that "exclusion powers are very serious and are not used lightly."

Prime Minister David Cameron, meanwhile, has called Trump's comment about Britain "divisive, stupid and wrong." But the Conservative Party leader has suggested the government won't ban him - arguing instead that a visit from the bombastic billionaire would "unite us all against him."

Despite Monday's debate, Parliament doesn't actually have the power to ban Trump. There won't even be a vote.

But Trump, who is of Scottish heritage, has not taken kindly to the debate. He has threatened to withdraw 1 billion dollars of planned investment in his Scottish golf courses if the government moves against him.

A travel ban, the Trump Organization said in a statement, "would send a terrible message to the world that the United Kingdom opposes free speech and has no interest in attracting inward investment."

Some in Parliament, while not siding with Trump, have argued that the debate is frivolous.

"The absurdity of Trump's candidacy is matched only by the fact that he is set to be the subject of a debate in the House of Commons," Jamie Reed, a Labour member of Parliament, wrote in a piece for Newsweek. "In the midst of so many domestic crises, this is a huge waste of U.K. taxpayers' money."

But the idea has attracted support from several prominent members, as well as from independent groups such as British Future, a migration-focused think tank. The group has noted that radical Islamist preachers and anti-Muslim bloggers, including Pamela Geller and Robert Spencer, have been banned.

"Trump's statements are more extreme than theirs," wrote British Future's director, Sunder Katwala.

Flynn, the member of Parliament who will present the petitioners' argument, said the difference between those cases and this one is that Trump "wants to be leader of the free world."

Selecting that leader, he said, is entirely up to U.S. voters. But if nothing else, he hopes that Monday's debate offers a reminder: "It's of huge consequence to the world who's living in the White House."