There was a time not that many years ago when it was impossible to imagine that the current Duchess of Cornwall could hold an honoured place in the Royal Family.

As Camilla Parker-Bowles, she was infamously dubbed "the Rottweiler" by Diana, Princess of Wales. The public didn't look kindly on Camilla either, considering her ongoing involvement with Prince Charles during his ultimately doomed marriage to Diana.

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Queen Elizabeth, right, Camilla, Duchess of Cornwall, centre, and Kate, Duchess of Cambridge stand outside the Fortnum and Mason department store in central London on March 1, 2012. (Alastair Grant/Associated Press)

Camilla "was seen as being the other woman in their marriage and at one point, it looked impossible that she would be integrated as a member of the Royal Family," says Carolyn Harris, a royal expert at Queen's University in Kingston, Ont.

Yet when Charles and Camilla — now a comfortably married, middle-aged couple — arrived in Canada on Sunday to mark the Queen's Diamond Jubilee, any air of tawdriness or tabloid titillation to their relationship had long gone.

In its place, Camilla appears as a loyal and supportive spouse who has her own interests and causes, and who has been formally honoured by the Queen.

In that transformation, from "other woman" to wife of the heir to the throne, lies a virtually unprecedented evolution, something observers see as the result of everything from the passage of time to a carefully managed campaign to bring Camilla into the royal fold.

"There are very few historical precedents for royal mistresses going on to become royal wives," says Harris.

So few that Harris goes back to the 1300s to find one of the most famous examples: John of Gaunt, Duke of Lancaster, the third son of Edward III and whose third wife was his mistress, Katherine Swynford. In the late 1520s, Henry VIII pursued Anne Boleyn while still married to Catherine of Aragon, but it's not clear if Anne had a physical relationship with him before she was sure he would marry her.

Passage of time

Camilla herself didn't go back quite so far in history on her first meeting with Prince Charles in 1970, apparently telling him, flirtatiously, that her great-grandmother, Alice Keppel, was the mistress of his great-great-grandfather, Edward VII, though the two never married.

Harris, who writes a blog called The Royal Historian, sees the passage of time and the reaction of Charles's sons as significant factors in the public acceptance of Camilla and the rehabilitation of her image.

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Prince Charles and Camilla, Duchess of Cornwall, leave St. George's Chapel in Windsor, England, following the church blessing of their civil wedding ceremony on April 9, 2005. (Alastair Grant/Associated Press)

"Something that I think has been crucial to that is that William and Harry's clear acceptance of her place in their father's life and how they want their father to be happy."

But Camilla's transformation owes itself to more than goodwill from her stepsons. Key to it was a careful public relations campaign that gradually brought Camilla into the public eye at Charles's side.

Alanna Glicksman, a Toronto public relations consultant, says the kind of evolution that's taken place around Camilla's public image is "something you do need a lot of help doing."

Toronto-born Mark Bolland, a public relations guru who served as deputy private secretary to Charles from 1997 until 2002, is widely seen as the architect of that transformation.

"He basically shaped how the public should see her," says Glicksman, whose blog The A List includes observations about the royals. "He found specific engagements for her to attend so she wasn't going everywhere left, right and centre."

Silence speaks volumes

Camilla's public silence through it all has also helped, Glicksman suggests.

"Camilla never reacted to any of the negative press that was said about her. She just let it slide, and by her not making it into a bigger issue, it also helped it go away faster."

And there was a lot of negative press.

Ninian Mellamphy, a professor emeritus at Western University in London, Ont., and a longtime royal watcher, says Camilla and Charles could hardly have embarked on a life together from a worse position, what with their own broken marriages, infidelities and so on. At that point, Camilla had quite an image to live down.

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Prince Charles and Camilla, Duchess of Cornwall, react as their car is attacked by angry protesters in London on Dec. 9, 2010. (Matt Dunham/Associated Press)

Since their marriage in 2005, "they've actually presented themselves as a fairly reliable and decent couple," Mellamphy says.

But he also sees other factors behind the changing public perception of Camilla, in particular instances that made her and Charles seem more like "real people." That included the time they were mobbed during a 2010 student riot in London and appeared more as "threatened people rather than people with kind of a mysterious and disapprovable past."

Word has also leaked out about a few health problems Camilla has had, and that "wins a certain type of sympathy," Mellamphy suggests.

Observers think Camilla has also had an effect on Charles, and the image he has with the public.

A softer side

"He seems to be a lot softer Prince Charles" these days, says Glicksman.

"If you go back to the royal wedding [of Prince William and Kate], there's a picture of him holding Camilla's granddaughter on the balcony. When you see Prince Charles, you might not always think warm and fuzzy, but Camilla seems to have brought that out."

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Camilla, on the set of Danish TV drama The Killing, holds a sweater from actress Sofie Grabol, left, as Danish Crown Princess Mary looks on in Lynge, Denmark on March 27, 2012. (Finn Frandsen/Associated Press)

Glicksman thinks Camilla's image has also softened considerably.

"She went from being the other woman to being a loving grandmother. She recently had an engagement where she read childrens' stories at a school and bystanders said she was very warm with the children and she was like a grandmother to them."

She's even looking a bit more cool, relatively speaking.

While it seems the House of Windsor is focusing efforts on making the younger generation of royals in particular seem hip, Camilla had her own brush with pop culture recently when she visited the set of the Danish cop show The Killing, which has quite a following in Britain.

Camilla may not be speaking publicly, but Glicksman thinks she is working hard to create the image the public now has of her, particularly because of the role in store for her when Charles ascends the throne.

"Especially if she is going to be the next queen, she has to be liked because this is the people's queen," says Glicksman.

"She wants to be liked and she's made sure that she's acted in a way that the British public forgets the past and focuses on the future."