British Prime Minister Theresa May invited United States president Donald Trump to parliament when she met him in Washington last month, just a week after he took office.
State visits are marked by much pageantry, traditionally including a carriage ride for the visiting head of state to Buckingham Palace to stay as a guest of the Queen.
But an online petition calling for Mr Trump to be allowed into Britain but not for a state visit has attracted almost 2 million signatures.
The huge number of signatures has prompted what is being touted as a symbolic debate in parliament.
While there would be no vote, and parliament has no power to stop the state visit, it was a chance for politicians to air their views on the US president.
Conservative Member of Parliament Mark Pritchard defended the state visit.
"The relationship, the special relationship, between the United Kingdom and the United States of America goes beyond any individual that might happen to occupy the White House at any particular time."
Theresa May's government wants to reaffirm that so-called special relationship with the United States and secure a trade deal as Britain prepares to leave the European Union.
But one female Member of Parliament questioned that support in parliament, suggesting Mr Trump's comments about women do not make him a suitable guest of the Queen.
"Does he agree that to use the expression 'Grab them by the pussy' describes a sexual assault and, therefore, suggests that he shouldn't be afforded a visit to our Queen?"
As parliament debated the state visit, protesters gathered in the thousands outside.
(Leader:) "Say, 'Hey!'"
(Crowd:) "Hey!"
(Leader:) "Say, 'Ho!'"
(Crowd:) "Ho!"
(All:) "Trump and Brexit got to go ... Say, 'Hey! Ho!' Trump and Brexit got to go."
Many held placards, bearing slogans such as "Love America, Hate Trump," "Resist the fake president" and "Theresa the Appeaser."
The Stop Trump Coalition, a collective of protest groups in Britain uniting against the possible visit, organised the demonstration.
It is yet another backlash Theresa May has to manage as she goes about trying to reunite the country divided over Brexit.
Opposition economic spokesman John McDonnell addressed the protesters, telling them Donald Trump does not deserve the honour of a state visit.
"We are calling upon the Government to withdraw the offer and make it absolutely clear. There is no way this honour should be made to someone who's abused women, who's abused members of the Muslim faith, who's abused migrants ..."
Ms May's office has said the state visit will go ahead but has not provided any details on what month Mr Trump will be invited nor the itinerary.
Meanwhile, the protests did not stop just in Britain.
Back in the United States, anti-Trump rallies have been held around the country to mark the public holiday known as President's Day.
Protesters took to the streets in about 28 cities to express displeasure with Mr Trump's policies and pronouncements.
But Mr Trump went about his daily business, naming Lieutenant General Herbert Raymond McMaster as his next National Security Adviser.
The widely respected military strategist told Mr Trump it is a privilege to serve the nation.
(McMaster:) "I'm grateful to you for that opportunity, and I look forward to joining the National Security team and doing everything I can to advance and protect the interests of the American people. Thank you very much, Sir."
(Trump:) "You're going to do a great job."
The announcement comes just days after General Michael Flynn resigned over questions about his ties to Russia.
