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LONDON — The planned state visit of President Donald Trump to the United Kingdom later this year could put 90-year-old Queen Elizabeth in a “very difficult position,” according to people in royal circles.

In a letter to the Times of London, Lord Ricketts, who was the permanent secretary at the Foreign Office (the British equivalent of the State Department) from 2006 to 2010, questioned whether Trump is “specially deserving of this exceptional honor?”

Ricketts said there is “no precedent for a U.S. president paying a state visit to this country in their first year. Most have had to wait till their third.” He added, “now the Queen is put in a very difficult position.”

In fact, if recent precedence says anything, former President Barack Obama made his first visit to the U.K. two months into office, but he did not receive the honor of a state visit until he had been in office for 28 months; and President George W. Bush made his first visit to the U.K. after six months, but he did not get a state visit until he had been in the White House for 32 months.

Queen Elizabeth II and US President Barack Obama arrive for a State Banquet at Buckingham Palace on May 24, 2011. Anwar Hussein / WireImage

In the U.K., the prime minister is the head of parliament and is in charge of the day-to-day running of the country, but Queen Elizabeth is the head of state. Therefore she is the person who officially receives foreign dignitaries.

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Invitations to a state visit are only granted on the advice of the Foreign and Commonwealth Office, and are viewed as an important instrument in the tool kit of international diplomacy — particularly because they involve all the pomp and circumstance of the royal family.

Leaders are given a grand ceremonial welcome by the Queen and other members of the royal family at Horse Guards Parade, a large parade ground in central London near Buckingham Palace. They are usually invited to travel from there to the Palace in a carriage escorted by soldiers mounted on horseback from the Household Cavalry.

The welcome is accompanied by gun salutes fired from Green Park and the Tower of London, according to the Royal Household website.

Queen Elizabeth II and President Vladimir Putin leave Buckingham Palace in London on June 27, 2003. AFP/Getty Images

The first day usually concludes with a lavish state banquet at Buckingham Palace with around 150 guests. For the remainder of their stay, the visitor usually meets with the prime minister and other government leaders.

But many are questioning if Trump should receive such a prestigious welcome so early on in his tenure as president.

As many as 1.6 million British citizens have signed a petition to Parliament saying that he “should not be invited to make an official State Visit because it would cause embarrassment to Her Majesty the Queen.”

British Prime Minister Theresa May announced during her visit to the White House last week that Trump had accepted an invitation from Queen Elizabeth II for a state visit later this year — reportedly in June.

Romanian dictator Nicolae Ceausescu rides in the state carriage with Queen Elizabeth II on his official visit to Britain on June 13, 1978. Getty Images

But that was before Trump announced his ban on immigration from seven predominantly Muslim countries — prompting swift international backlash.

Thousands demonstrated against Trump’s executive order in London on Monday night outside the Prime Minister’s home at 10 Downing St.

This wouldn't be the first time the Queen met with a figure unpopular on the world scene. After 60 years as the reigning monarch, she’s seen them all: She welcomed the first Communist head of state, Romania’s Nicolae Ceausescu, in 1978 when he was already well-known as a corrupt and oppressive leader, as well as Zimbabwe’s Robert Mugabe in 1994.

President Robert Mugabe of Zimbabwe is greeted by Queen Elizabeth ll and Prince Phillip the Duke of Edinburgh at Buckingham Palace during his State Visit to London, England, on May 1, 1994. Anwar Hussein / Getty Images

To Camilla Tominey, Royal Editor at the Sunday Express, differences of opinion are par for the course and don’t make for a bad state visit.

“To be honest, the queen is probably one of the world’s best diplomats. She knows how to behave,” Tominey told NBC News on Tuesday. “She’s met 10 U.S. presidents. The eleventh might raise an eyebrow, but it will be ‘Keep calm, carry on,’ business as usual, because that’s what state visits are all about: diplomacy.”

And as Tominey pointed out, the royals have done this before.

“And at the end of the day, the royals haven’t got where they are by jumping on single issues and making a political point,” she added. “They are there, they are the constant, they are the diplomats, they are the receiving party."

And May is standing by her invitation, citing the close relationship between America and Britain.

“The United States is a close ally of the United Kingdom. We work together across many areas of mutual interest and we have that special relationship between us,” May said Monday during a joint press conference in Dublin with Ireland's head of government, Enda Kenny. “I have issued that invitation for a state visit for President Trump to the United Kingdom, and that invitation stands.”