A fairy tale, it was not.

But that’s how it looked when Diana Spencer walked down the aisle in a 25-foot train to marry her prince in 1981, a girl of 20 seemingly destined to become queen.

With an estimated 750 million people around the world watching, the fresh-faced Diana said "I do" to 32-year-old Prince Charles.

But their 15-year marriage  was doomed from the start. As the public would come to find out (in tabloid nirvana for the British media) Charles’ heart was tied up with Camilla Shand, a woman he’d met over a decade prior in 1970.

Why wasn't she the one, then? Blame her less-than-royal credentials. Camilla lacked an aristocratic bloodline and wasn’t viewed as “virginal” enough for a proper courtship and role as a royal wife.

And so Camilla moved on first, marrying Andrew Parker Bowles while Charles was off serving in the Royal Navy. The devastated prince remained close friends with Camilla (rekindling an affair with her in the late 1970s), until finally moving on in 1981 with the beautiful, young and blond Lady Diana Spencer, the 19-year-old daughter of an earl from a family older than the Windsors. (A bit of trivia: Charles also dated Diana's older sister, Sarah in 1977, ending the relationship after she engaged with the press.)

Was it real? A reporter asked the pair if they were in love in 1981. "Of course," replied a demure Diana. "Whatever 'in love' means," added Charles. Ouch. The couple famously only saw each other about a dozen times before they married.

The couple's much-watched first few years building a family were relatively stable, but in 1986, after his two sons, Prince William (now 35) and Prince Harry (32) were born, Prince Charles rekindled his affair with Camilla. In retaliation, Diana began a five-year affair with her riding instructor, James Hewitt.

In 1995, BBC journalist Martin Bashir asked Princess Diana if she believed Camilla contributed to the breakdown of her marriage. “Well, there were three of us in this marriage, so it was a bit crowded,” she famously replied. 

And Diana told biographer Andrew Morton she once confronted Camilla. “I know what's going on between you and Charles and I just want you to know that,'" recalled Diana said on the tapes recorded for Morton, whose 1992 book, Diana: Her True Story, blew open for the public the secret of the Wales' failing marriage.

"She said to me: 'You've got everything you ever wanted. You've got all the men in the world fall in love with you and you've got two beautiful children, what more do you want?' So I said, 'I want my husband'. And I said, 'I'm sorry I'm in the way ... and it must be hell for both of you. But I do know what's going on. Don't treat me like an idiot.'"

The royal couple separated in 1992 and divorced in 1996. More than 30 years after their relationship began, Prince Charles married Camilla in 2005.

The brief civil ceremony in the Windsor town hall was remarkable: Never before has a future king married a divorced woman; never before has a woman married a Prince of Wales and taken a lesser title than princess (Camilla was named Duchess of Cornwall).

Though Queen Elizabeth II and Prince Philip did not attend the modest, low-key, no-frills civil ceremony, they did attend a blessing service at Windsor Castle's  St. George's Chapel  that followed and hosted a reception for about 800 people afterward.

In the 12 years since, Charles’ second wife has quietly earned the public’s trust after a rocky beginning to her public life caused by her relationship with Charles during his unhappy marriage to the late Princess Diana.

Once known as the "most hated woman in Britain," a decade later the British public has come around, according to polling conducted for CNN in 2015.

The poll found that opposition to Camilla eventually being called Queen Camilla — once as high as 73% — had dropped to 35% , and nearly one in four Brits said they liked her more now than they did 10 years prior.

"It's always marvelous to have somebody who, you know, you feel understands and wants to encourage," Prince Charles told CNN." Although she certainly pokes fun if I get too serious about things. And all that helps."

 

Contributing: Maria Puente