Maybe they're already secretly engaged. Or maybe not. 

Breathless headlines have speculated for months on whether — or when — Prince Harry and his girlfriend, Toronto-based, California-born actress Meghan Markle, might announce a royal wedding is in the cards.

Swirling speculation around high-profile Royal Family members is nothing new, but the way in which this relationship has evolved in public appears to have broken new ground on many fronts.

"What's interesting about Prince Harry and Meghan Markle's relationship is that there have been milestones that often we do not see until after a royal engagement," says Carolyn Harris, a Toronto-based royal historian and author.

They've openly spoken about the relationship. Harry, 33, talks about Meghan, 36, as his girlfriend. She has talked about how she feels about him — in a cover story in Vanity Fair. In their first public appearance together, they showed up holding hands during the Invictus Games in Toronto in September.

Invictus Games Wheelchair Tennis TOPIX 20170925

Harry and Markle arrived hand in hand at Nathan Phillips Square in downtown Toronto. (Nathan Denette/Canadian Press)

"In many ways, in terms of their public image, they're behaving as an engaged royal couple," says Harris, whose book Raising Royalty: 1,000 Years of Royal Parenting, was published earlier this year.

But so far, it's been radio silence from official channels on the possibility of an engagement.

The tabloids — and even some of the more restrained media outlets — have been paying close attention, though, with speculation suggesting an engagement might be announced before the end of this year, with a wedding in spring or early summer of 2018.

'I have no idea'

Then again, another report in the Daily Beast this month, quoting a "source with excellent contacts in the palace," suggested no announcement would be forthcoming before Harry's sister-in-law, Kate, the Duchess of Cambridge, has her third baby, due in April.

Those who watch these things closely hesitate to make definitive statements.

"I have no idea, I'm afraid," U.K.-based royal biographer Penny Junor says when she considers whether an engagement is inevitable or has already happened, as some tabloids have suggested, particularly after Harry spirited Markle away for an African holiday in August.

"It would be a huge change for her," says Junor, author of the biography Prince Harry Brother Soldier Son.

Britain Prince Harry

Markle participates in AOL's BUILD Speaker Series in New York on March 17, 2016, to discuss her role on the television show Suits. (Evan Agostini/Invision/Associated Press)

"She's got a very independent life and it would be a massive change. I don't think we should assume she's just waiting for the proposal."

Junor cautions that breathless headlines about a possible royal engagement are nothing new. Consider the media attention on Harry's father, Prince Charles, in the 1970s.

"They had him married off to all sorts of people, including Princess Marie Astrid of Luxembourg, whom he'd never even met."

'Very much in love'

Still, Junor figures there's "a lot more going on here" with Meghan and Harry.

"If the way they behave with one another is anything to go by, they are very much in love with each other."

Author and royal biographer Sally Bedell Smith also sees signs that could point toward an engagement.

She hesitates to say too much without direct knowledge, but thinks "it's reasonable to see a pattern in events over the past year." Markle stopped posting on her Instagram account last spring, and shut down her lifestyle blog, The Tig.

There have been further "baby steps," Smith says, noting public appearances with Harry and the "giant step of the Vanity Fair interview, evidently sanctioned by Prince Harry and Kensington Palace."

Since then, there were her appearances with Harry at the Invictus Games, and reports he took her to tea with his grandmother, Queen Elizabeth, at Buckingham Palace.

"All arrows seem to point in one direction, much as they did during previous pre-engagement rollouts for Camilla Parker Bowles and Kate Middleton," says Smith, referencing the time before the announcements of Camilla's engagement to Charles in 2005, and Kate's to Harry's brother, Prince William. The announcement of that engagement came seven years ago today, on Nov. 16, 2010.

'On their own terms'

If an engagement is forthcoming for Harry and Markle, it's not likely to be long.

"Past precedence would indicate that once an engagement's announced, a royal wedding will be imminent after that,"  says Harris.

But what kind of wedding might it be?

Not likely one that would rival those of Harry's father or brother.

Weddings Headpieces

If Prince Harry and Meghan Markle do marry, it's unlikely their wedding would be as elaborate as the ceremony for his elder brother, Prince William, and Kate Middleton, who were married on April 29, 2011, at Westminster Abbey. (Martin Meissner/Associated Press)

"She is a divorcee, so I don't think there would be the kind of fairy-tale wedding that Charles and Diana had or even William and Kate," says Junor.

That there is open speculation of a divorced woman joining the Royal Family is also a reflection of changing times. Back up two generations, and Princess Margaret, the Queen's sister, was forbidden from marrying a divorced man.

'Reflection of society'

"So times have changed enormously … now we have three of the Queen's children divorced and two of them remarried, and the heir to the throne and his wife are both divorced people, so it's a reflection of society today," says Junor.

"Harry hitching up with Meghan is very much in keeping with all that, and I think it's important for the Royal Family not to be seen to be weird creatures from some other planet, living in a time warp."

And what about after a wedding?

"If Meghan and Harry get married, I think they'll have considerably more latitude in how they go about their life together," says Smith.

"I wouldn't be surprised, for example, to see them spend time in California as well as the U.K."

Junor says the only thing that worries her is the possibility Markle would have to give up her work.

"She probably would, in reality, because people when they marry into the Royal Family marry into a business, a firm, and I don't know how easy Meghan would find that, because she does have a very successful career."

Accustomed to the spotlight

Still, as an actress, she is accustomed to the spotlight, and has been involved in philanthropic endeavours — a priority for many members of the Royal Family.

"Meghan has a long and earnest involvement in charitable causes, so that piece should be the easiest for her," says Smith.

But what about living as a royal?

"It will be trickier for her to master the subtleties of life inside the Royal Family — the traditions, the protocol, the nomenclature, the nuances," says Smith.

Of course, media speculation has already focused on how Markle might be preparing for that life. Some headlines suggest she has had "princess lessons."

In that, the speculation takes a sharp turn from informed commentary.

"There's definitely this popular speculation as to what happens when someone who is not from a royal or aristocratic background marries into the Royal Family," says Harris, "and often a lot of the classic fairy-tale plot lines inform the speculation."