President Donald Trump tweeted Thursday that he won't be visiting London to open the new, relocated billion-dollar U.S. embassy, because he didn't want to be associated with what he called a bad real estate deal made under the Obama administration.

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Here are seven things to know about the embassy and Trump's now canceled visit to London:

1. The decision to relocate the London embassy was actually made under former President George W. Bush.

According to the embassy website, the decision to move the location was made months before former President Barack Obama took office in January 2009.

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2. The embassy was relocated due to security reasons.

The old United States Embassy in Grosvenor Square in the historic Mayfair neighborhood was deemed to be vulnerable to terrorist attacks, the New York Times reported.

"Security concerns after September 11 meant we had to move to a location that could better protect American citizens and our British neighbours," Trump's diplomatic appointee to the U.K., businessman and New York Jets owner Robert "Woody" Johnson wrote in the U.K.'s Evening Standard.  "It is the most secure, hi-tech and environmentally friendly embassy that the United States has ever built," he said about the new site.

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When the decision was made years ago to relocate from prime real estate to a former railyard in the “gritty” district of Nine Elms, some local officials were critical.

"It seems sad that the U.S. Embassy is relocating from a beautiful historic square in Mayfair to a fortified bunker in former railyards on the far side of the river," Peter Rees, the City of London's former head of planning, told the Times in an email in 2015. "It's like moving from New York's Upper East Side to New Jersey."

The Qatari royal family’s property company has now taken over the site in the Mayfair neighborhood of central London. The family plans to convert it into a luxury hotel.

The new embassy is estimated to have cost $1 billion — “in the ballpark of the most expensive embassies we have built,” former acting director of the Bureau of Obverseas Buildings Operations Adam Namm told the Times.

From a 2015 New York Times report:

“The 4.9-acre site will have a public plaza featuring a pond, walkways connecting to the planned Tube stations and seating. Metal barriers will be replaced by grass berms, low garden walls and benches. Two small meadows on one side of the chancery will serve as a setback, as will the pond, essentially a moat, euphemistically described by American officials as a ‘water feature.’”

3. Trump accused Obama of selling off "perhaps the best located and finest embassy in London for peanuts, only to build a new one in an off location for 1.2 billion dollars." But the selling price was never actually disclosed.

According to the Indepdent, the selling price was never disclosed but estimates put the value of the sale at about $687 million, considerably more than the site actually cost ($1.2 billion). "It's hard to describe half a billion pounds as 'peanuts,' the British newspaper wrote.

4. Trump accepted a state visit offer last year.

According to the New York Times, British Prime Minister Theresa May invited Trump to Britain for a state visit last year, and he accepted.

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“Such an honor is normally bestowed only much later in a presidency,” the Times reported.

But no official statement had been made about the embassy visit.

With the U.K. to leave the European Union in 2019, May hoped  to “negotiate a new trade agreement with the United States, and the state visit was partly seen as a way of cementing ties with” Trump, according to the Times.

5. More than one million people signed a petition for the invitation to be withdrawn.

Trump’s often controversial comments on a range of topics — including the time he retweeted a far-right group’s anti-Muslim video in November and when he denounced London Mayor Sadiq Khan for doing nothing to combat terrorism — have outraged many in the U.K.

A petition calling for May’s invitation to be withdrawn at the time of a May state visit between Trump and Queen Elizabeth II garnered more than 1.8 million signatures, the Times reported.

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6. Critics said Trump's embassy visit cancellation is actually a cover for what would have been a troublesome visit.

Instead, critics say his decision to cancel is likely due to the fear of angry anti-Trump protests and his rocky relationship with May.

Former Labour Party leader Ed Miliband responded to Trump on Twitter and said, “Nope. It’s because nobody wanted you to come.”

London mayor Sadiq Khan chimed in, too.

And David Lammy, a lawmaker for the opposition Labour Party, said Trump was shaken by the prospect of being "met by millions of us out on the streets protesting," the Washington Post reported.

Additionally, Trump’s relationship with May is somewhat confusing.

“There was the attempt to rush over to the U.S. to embrace him, then she became implicated in the things he was doing, and then she had to pull back, so she’s been zigzagging,” Mark Leonard, director of the European Council on Foreign Relations, told the New York Times.

Trump has publicly rebuked May in the past, most notably over her criticism of anti-Muslim propaganda and her defense of London Mayor Sadiq Khan when Trump criticized him.

A spokesman for May last month rebuked Trump, saying he was "wrong" to have shared the videos, prompting Trump to lash back at the prime minister, AP reported.

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7. Many believe Trump's comments canceling the visit deepen diplomatic problems between the Britain and the U.S.

The U.K. has long been considered one of America's biggest allies. The late U.K. Prime Minister Winston Churchill even called the bond between the countries the "special relationship. But many feel Trump's embassy visit cancellation have further strained ties.

“It’s disappointing. He’s been to countries all over the world and yet he’s not been to the one with whom he’s closest. I would say it’s disappointing,” one of Trump’s most  vocal supporters in Britain, Nigel Farage, former leader of the United Kingdom Independence Party, told the BBC. “But maybe, just maybe, Sadiq Khan, Jeremy Corbyn and the Labour Party planning mass protests, maybe those optics he didn’t like the look of.”

Britain Foreign Secretary Boris Johnson accused the Labour Party leaders of putting the U.S.-U.K. relationship at risk.