Obama or Trump at royal wedding? Why Prince Harry and Meghan's guest list may not get too political

The guest list for any wedding can be a minefield, fraught with the challenges of navigating messy family relationships or trying to keep numbers down to what can be accommodated at the church or hall.

So it's likely there's considerable debate unfolding at Kensingtonand Buckingham palacesas names are bandied about for the list of who will attend when Prince Harry marries Meghan Markle at Windsor Castle on May 19.

• Read CBC's complete coverage of the royal wedding

But beyond deliberations over which relatives and friends of the fifth in line to the throne and his American fiance will get a seat in St. George's Chapel, there is also the question of how diplomacy and politics may play out in the list.

For Harry and Meghan, there's a strong likelihood there may be fewer geopolitical considerations than there have been for other royal weddings.

In the past, putting a royal wedding guest list together has depended on the ceremony's locationand"on the royal couple's place in the succession," says Carolyn Harris, a Toronto-based royal historian and author.

The higher they are, the greater the consideration that's paid to the "political and diplomatic aspects of the guest list," says Harris, author of Raising Royalty, 1,000 Years of Royal Parenting.

• Harry, Meghan make 1st official joint tour
• Meghan could nudge House of Windsor into future

Harry sits at No. 5, so doesn't rival the level of his father, Prince Charles, who's first in line to the throne, or his older brother William, who is No. 2. Numbers three and four are William's children George and Charlotte. (Harry will slip to sixth in line when William and Kate's third child is born in April.)

Still, speculation has swirled about whether a former U.S. president and high-profile friend of Harry Barack Obama might snag an invitation, and whether the current president Donald Trump might get his nose out of joint if Obama is invited and he isn't. U.K. media reports suggestthe British government isworried.

Harry somewhat dodged the Obama question a couple of weeks ago.

What if he's snubbed?

On the Trump front, Fire and Fury author Michael Wolff stirred the pot when he said a post-Brexit trade deal between the U.K. and the U.S. could be at risk if the American president, who doesn't like being snubbed, isn't on the May 19 list.

"Trump's foreign policy doctrine is simple: you Brits suck up to him and enlist in whatever geopolitical fantasy he has going, he'll give you what you want though only if it doesn't hurt him," Wolff told the Mail on Sunday newspaper.

But could the royal wedding guest list really affect how trade evolves between two longtime allies?

"It sounds incredibly unlikely, I think, not least because the time scales are so very different," says Simon Usherwood, deputy director of the U.K. in a Changing Europe program based at King's College London.

The wedding is four months away. Brexit and trade agreements are much further down the road.

"If there is offence taken at not being invited to the wedding, that can be more than offset by having the state visit that has been long discussed since Trump's election," says Usherwood, a researcher in European politics at the University of Surrey.

It's widely thought Trump is unlikely to be invited. And even if he did take offence over that, would it matter years later when trade talks would be more front and centre?

"I think a large part of what has been said is that [Trump's] attention span is relatively short and whilst it might cause offence one day, the next day things might be fine again," says Usherwood.

Waving the flags

The spectre of major politics playing out atthe wedding is not one the House of Windsor is likely to want.

"You can imagine that people in the royal establishment might be concerned that you've got protesters lining the streets in Windsor protesting the presence of certain individuals on the guest list rather than waving Union Jacks and being happy for the couple," says Usherwood.

Still, politics is a pervasive beast and has found its way into royal weddings.

Queen Victoria married in 1840 in the relatively small venue of the Chapel Royal at St. James's Palace in London.

Victoria thought highly of the Whig prime minister of the day, Lord Melbourne, and guests included many Whig politicians. Tory politicians were few and far between.

"The guest list was seen as making [Victoria's] sympathies very clear, and as a constitutional monarch she was expected to be above politics," says Harris.

More than a century later, the guest list for the 1947 wedding of the current Queen Elizabeth and Prince Philip Harry's grandparents was notable for some absences.

No uncle, no sisters

Elizabeth's uncle, the Duke of Windsor, wasn't at Westminster Abbey, with feelings still raw 11 years after the Duke, as King Edward VIII, had abdicated.

"In Prince Philip's case, his sisters were not invited to the wedding, as they were married to German princes who had been involved in the Nazi party during World War Two," said Harris.

When Harry's parents, Prince Charles and Lady Diana Spencer, married in 1981, the ceremony was at the larger St. Paul's Cathedral.

"With the marriage of the heir to the throne, as Prince Charles has been for most of his life it was considered important that there be a large venue that could accommodate as wide a range of guests of possible, including diplomatic guests," says Harris.

Three decades later, William married Kate Middleton at Westminster Abbey. That guest list involved a major rewrite, after William tore up the first official one he was given.

"There was very much a subdued moment when I was handed a list with 777 names on not one person I knew or Catherine knew," William said in an ITV1 documentary, according to a report in the Guardian newspaper.

"I went to her [the Queen] and said: 'Listen, I've got this list, not one person I know. What do I do?' and she went: 'Get rid of it. Start from your friends and then we'll add those we need to in due course. It's your day.'"

Many friends of the couple attended on April 29, 2011,as did representatives of royal families from across Europe. There was a Commonwealth and Canadian presence, as would be expected and is likely again in May.

No Obama last time

Canada's governor general at the time, David Johnston, attended in 2011. Prime Minister Stephen Harper was invited, but chose to stay home because a federal election was coming three days later.

The U.S. president of the day Obama wasn't invited.

"In the past, if you were a younger heir or second-in-line to the throne, you might not have got much say over your guest list," says Harris, but "William and Kate's experience indicated that the trend is now toward the bride and groom having more influence over the guest list itself."

The venue for Harry and Meghan, and its relatively smaller size as royal wedding locales goes, also suggest there may not be that many politicians there.

Ceremonies at those smaller venues, including that of Harry's uncle, Prince Edward, at St. George's Chapel in 1999, have often been"notable for the absence of political figures," says Harris.

Still, every wedding is different. And the fact that Meghan is American adds a wrinkle.

"At some point, an accommodation will have to be found," says Usherwood.

"You would imagine there would be a representative of the U.S., but that doesn't have to be the president and there are lots of other people who can do that."

Sign up for the Royal Fascinatornewsletter: Your invitation to royal wedding news and analysis ahead of Prince Harry and Meghan Markle's nuptials, delivered to your inbox.