When Meghan Markle weds Prince Harry she will be the first American to become a member of the Royal Family. The forming of such an historic transatlantic union would, on the face of it, be an apposite occasion for the US President to attend.
Kensington Palace said today the guest list is in the early stages of being compiled and that the Prince and Miss Markle would have the primary input, reports The Telegraph.
Yet a former senior UK diplomatic source told the Telegraph he would be "surprised" if President Trump received an invitation to the royal wedding in May.
There are a number of stumbling blocks to Mr Trump receiving an invite, not least Miss Markle's own public views about the President and the potential controversy he could bring to the happy occasion.
There is a precedent for US presidents not attending royal weddings. When the Duke and Duchess of Cambridge married in 2011 many heads of state attended, but the majority were from Commonwealth and European nations.
President Obama was not invited to the wedding on account of the added security costs his presence would have brought. Although Mr Obama did have a state visit to the UK less than a month after the wedding, which included a state dinner with the Queen at Buckingham Palace.
Likewise, President Ronald Reagan did not attend the wedding of Prince Harry's parents, the Prince of Wales and Princess Diana, in 1981 as he was recovering from an assassination attempt four months earlier. Yet his wife, Nancy, who was a close friend of the Prince, did attend alone.
Miss Markle's comments on President Trump
Another potential hurdle to Mr Trump making the guest list is the fact Miss Markle has been an outspoken critic of the Republican in the past.
In a 2016 appearance on The Nightly Show with Larry Wilmore the Suits actress described Mr Trump as "divisive" and "misogynistic".
She said: "Yes of course Trump is divisive, think of just female voters alone, right. I think it was in 2012 that the Republican party lost the female vote by 12 points.
"That's a huge number and with as misogynistic as Trump is and so vocal about it, that's a huge chunk of it.
"You're not just voting for a woman, if it's Hillary, just because she's a woman, but certainly as Trump has made it easy to see that you don't really want that kind of world."
Also in the interview, Miss Markle said she "might just stay in Canada", where she was filming Suits if Mr Trump won the presidential election.
Stalled state visit
The complications and controversy caused by the planned state visit for President Trump present another potential roadblock to any invitation.
Within days of Mr Trump's inauguration, Theresa May was the first world leader to visit him in Washington, where she offered the new president the prospect of a full state visit to the UK. The move prompted a strong backlash from MPs across the political spectrum and the Commons Speaker, John Bercow, announced he would oppose any plans for the President to address Parliament.
Another fear was that Mr Trump's presence on UK soil could prompt large-scale protests and cause more harm to relations with the President.
Plans for Mr Trump to visit the UK have since been quietly downgraded to a "working" trip that would not see him meet the Queen or stay at Buckingham Palace.
If Mr Trump were to attend the royal wedding it could be the catalyst for large demonstrations that would tarnish the jubilant occasion.
Mr Trump's tenure in the White House has been beset with controversies, some of which have roiled public opinion on this side of the Atlantic. This week he retweeted a number of anti-Islamic videos from the far-right Britain First group.
His actions were criticised by Brendan Cox, the widower of MP Jo Cox who was slain by a man who shouted "Britain first" as he attacked her. Mr Cox said Mr Trump had "legitimised" the far right and accused him of "spreading hate".
The retweets provoked an angry response from MPs and renewed demands that the offer of a state visit be withdrawn from President Trump.
Previous comments about the Royal Family
Another potential bar to Mr Trump getting an invitation is his record of making unflattering comments about members of the Royal Family. In 2000 he made extremely vulgar remarks about Prince Harry's mother, Princess Diana, on a US radio show.
The real estate mogul also publicly criticised Prince Harry's sister-in-law, the Duchess of Cambridge, after she was photographed topless by French paparazzi while on holiday in Provence in 2012. Earlier this year Closer magazine was ordered to pay €100,000 to the Duchess by a French court for breaching her privacy.
At the time the story broke, Mr Trump went onto the Fox News channel and criticised the Duchess, saying: "How can you do a thing so stupid".
If not Mr Trump, then maybe Mr Obama?
If Mr Trump doesn't receive an invite the royal wedding, there's a chance his predecessor, Barack Obama, may make the guest list. The former president and his wife, Michelle, have formed a close relationship with Prince Harry and they have been seen together a number times since he left office.
In May the Prince hosted Mr Obama at Kensington Palace during his visit to the UK and in September the pair were seen laughing and joking together while watching wheelchair basketball at the Invictus Games. Then last month the Prince appeared with Michelle Obama at a charity event in Chicago.
The Duke and Duchess of Cambridge invited a number of celebrity friends to their wedding, including David and Victoria Beckham.
Meanwhile it has been noticed that while Mr Obama offered the Prince and Miss Markle fulsome congratulations on their engagement, Mr Trump has been conspicuously silent on the matter.