Meghan Markle got the British tabloids in a tizzy a few days ago when she showed up to cheer on her royal boyfriend, Prince Harry, at a charity polo match outside London.

Even some of the more restrained media outlets drew attention to the Toronto-based Markle's first semi-official appearance in public with the fifth in line to the throne.

Underlying it all is the question that has followed the two since their relationship was publicly confirmed last fall: Is a royal wedding in the offing for the 32-year-old former party prince and the 35-year-old American actress he reportedly met in Toronto last year?

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Harry takes part in the annual Audi Polo Challenge at Coworth Park polo club in Ascot, England, on May 6. (Steve Parsons/PA/Associated Press)

Royal observers hesitate to offer a definitive answer on the wedding question — nothing's for certain until there's an engagement announcement from Buckingham Palace. But signs suggest the relationship is more than a passing fancy.

Markle's appearance at the polo match shows "the seriousness of the relationship," says Toronto-based royal historian and author Carolyn Harris, who also points to the statement Harry put out last fall urging the media to back off from Markle and give her privacy.

"It's very striking for there to be an announcement of who a senior member of the Royal Family is dating, because in the past that hasn't been the convention."

If the relationship is serious, and Meghan and Harry end up walking down the aisle, it will signal another subtle shift for the House of Windsor, which has been trying to put a more modern face on the monarchy.

"If Harry were to marry Meghan, it would show how far the Royal Family has come in its willingness to embrace spouses who are not from the English upper class and to put a higher premium on love and compatibility than on suitability according to an archaic standard," says Sally Bedell Smith, an author whose biography of Harry's father, Prince Charles, was just released.

Kate came first

Smith sees the first step in that willingness coming with Kate Middleton, a woman from a "solid middle class family with working class roots" who married Harry's older brother, Prince William, in 2011.

"Now comes Meghan Markle," says Smith, "a California girl who is proudly biracial — with an African-American mother and white father — and a graduate of top-flight Northwestern University who made her career as a successful actress by dint of hard work."

There's a marked difference, Smith suggests, between Harry and Meghan and the previous generation.

"It is hard to imagine that Harry's father was compelled in 1981 to marry a woman from an aristocratic family who at least appeared to be virginal."

That marriage — of Charles to Lady Diana Spencer — ultimately descended into tabloid tawdriness before ending in divorce in 1996, a year before Diana died after a car crash in Paris.

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Harry's parents Prince Charles and Lady Diana Spencer were married on July 29, 1981, but the marriage ended in divorce 15 years later. (Reuters)

Years ago, Markle would have been an unlikely candidate as a potential royal spouse, particularly given her previous divorce. She's also American, which hasn't always gone down that well with the royals. But neither factor seems as critical now.

"Times have changed from the days when Edward VIII had to abdicate in order to keep the American divorcee [Wallis Simpson] he loved. It is no longer a problem to be either," says Penny Junor, U.K.-based author of the 2014 biography Prince Harry: Brother, Soldier, Son.

When Charles married again in 2005, it was to Camilla Parker Bowles, who had been involved with Charles for years and divorced from her first husband a decade earlier.

'Softening of attitudes'

"That's been widely seen as a softening of attitudes toward members of the Royal Family marrying divorcees," says Harris.

Other royal families in Europe are "even more relaxed about the whole question of who's a suitable spouse for royalty," says Harris, noting, for example, that Crown Prince Haakon of Norway married a single mother.

Harris, whose book Raising Royalty: 1,000 years of Royal Parenting was just released, sees whomever Harry marries as being part of a streamlined Royal Family, a move that was signalled particularly in the Queen's Diamond Jubilee celebrations in 2012.

At that time, the emphasis was on the Queen and her husband, Prince Philip, (whose retirement from public duties was announced last week), Charles and Camilla, William and Kate, and Harry, rather than a more extended family including cousins who have carried out royal duties.

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Markle discusses her role on the television show Suits in New York City on March 17, 2016. (Evan Agostini/Invision/Associated Press)

"There's going to be expectations that anyone Prince Harry marries is going to take on many charitable patronages and be interested in undertaking overseas tours," says Harris.

Markle could have at least one thing in her favour in that regard. She has been involved in humanitarian work for various organizations including World Vision Canada, the United Nations and One Young World.

"She is already involved with gender equality and the empowerment of women, and the clean water campaign, so the welfare [and] charitable aspects of royal life would come very easily to her," says Junor.

Markle has commented on her humanitarian efforts, saying: "While my life shifts from refugee camps to red carpets, I choose them both because these worlds can, in fact, co-exist. And for me, they must," the Daily Telegraph reported.

Given Markle's interests, Junor thinks she could fit into a "modern model" of the Royal Family quite easily.

Farewell to The Tig

"Who knows quite what the Royal Family will look like in the future. It may well be that it could accommodate someone with a successful career married to the fifth in line to the throne," says Junor.

"I think that could be a very good thing. It would certainly stop the constant complaint that the family are a drain on public funds."

Royal watchers looking for any clue about the seriousness of Markle's relationship with Harry wondered what signals if any might be read into her recent decision to shut down her lifestyle website, The Tig. There have also been no new posts on her Twitter feed since March 8.

'Excessive communication with the media has ended royal relationships.' - Carolyn Harris

Harris says that, in the past, discretion has been "very key to being associated with royalty."

"Excessive communication with the media has ended royal relationships," she says, pointing to Prince Charles dating Diana's elder sister, Sarah.

"Then she spoke to the press about her friendship with [Prince Charles] and that certainly was not considered a great decision to make."

Shorter horizon?

While a proposal wouldn't be that surprising, there is no sense of when one might come.

"William and Kate had eight years of living together to develop a mature relationship," says Smith. "I suspect that because Harry is nearly 33, and Meghan is almost 36, that their time horizon before marriage would have to be shorter."

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Toronto Mayor John Tory, left, Prince Harry and Prime Minister Justin Trudeau celebrate a goal during a sledge hockey game during Harry's visit to Toronto last year to promote the 2017 Invictus Games, which the city will be hosting. (Nathan Denette/Canadian Press)

Junor guesses an engagement could come toward the end of this year, but not before Harry is back in Toronto in September for the Invictus Games, the international adaptive sporting event he founded for wounded, injured and sick soldiers and veterans.

"He wouldn't want to overshadow the athletes."