1986, London, England, UK --- Prince Andrew is seen kissing Sarah Ferguson on the balcony, after their wedding ceremony at Buckingham Palace in this photo. Queen Elizabeth II and Prince Edward stand to the right of the couple. --- Image by Bettmann/CORBIS

There could have been no clearer demonstration of the continuing contempt in which Fergie – or rather ‘The Duchess’ as she insists on being referred to despite the ‘Call me Sarah’ attitude always on display during TV interviews – was held than when the invites for William and Kate’s wedding were sent out in 2011.

Astonishingly, among the thousand-plus invitees, Sarah Ferguson’s name was not on the list. The royals hate Fergie, and they are not afraid of showing it.

But now, in an astonishing reversal of fortune for the loud-mouthed red-head who became the bane of the British establishment, Fergie has been invited back to the Queen’s Scottish estate, Balmoral, for the first time in twenty years - and the British press was swirling this weekend with amazing rumors that she and Andrew have re-ignited their romantic relationship and may even be planning to remarry.

According to the reliable diarist Richard Eden in the Telegraph, friends of the couple, who still live in the same house, are speculating that they will indeed “formalize” their relationship.

“Mark my words, they will remarry, it is only a matter of time,” one friend tells Eden while another said: “It wouldn’t surprise me at all. They are a wonderful couple together and, better still, pretty amazing parents.”

While some will dismiss the marriage talk as pure speculation (Fergie’s people have moved quickly to deny it, insisting that the couple are just good friends) what is not in dispute is that the visit to Balmoral earlier this month is a major gesture of good will from the Queen.

It is possible that the ever-practical Queen invited Fergie to Scotland because the next royal wedding could well be between Beatrice (the Queen's favourite grandchild) and her boyfriend Dave Clark, and, well, they couldn’t really ban Fergie from that one, could they? So maybe best to do the awkward raprochement behind closed doors, rather than on the church steps.

While many assume that the royals coolness for Fergie goes back to the scandal when her American financial adviser John Bryan was photographed sucking her toes in 1992 (Fergie found the family reading about the scandal in the papers as she came down to breakfast at Balmoral one morning) the truth is more complicated than that.

Although there is no doubt that the pictures were embarrassing, the royals are actually pretty forgiving of press scandals, tending to close ranks and blame the filthy ink-stained wretches. Fergie and Andrew were already seperated at the time of the incident.

Fergie did something much, much worse than have a fling - she told the family's secrets. The real damage to the relationship was done after her  divorce to Prince Andrew the following year; the publication of a tell-all book, the television interviews, the attempts to trade off her name in an ever more disastrous series of business deals that left her a reported $5m in debt and, finally, in the greatest humiliation of all, she was filmed trying to sell access to her former husband, Prince Andrew, in his capacity as trade ambassador, to a journalist at the now defunct News of the World in 2010.

The betrayal was all the more sickening because throughout her difficulties Andrew had nobly supported his errant former wife, providing her, controversially  with a set of rooms at his home, Royal Lodge, in Windsor Great Park, and never criticising her even in private.

She was clearly drunk in the film, but has since stopped drinking.

Shortly after her encounter with the News of the Screws, her invitation to the wedding of the century failed to appear.

Sarah’s greatest enemy in the royal fold was undoubtedly Prince Philip. Philip remains to this day staggered by his second son’s forgiving attitude towards his former wife, and the feeling is mutual; Fergie relentlessly briefs against him in private. No surprise, therefore, that Fergie’s stay at Balmoral came to an end before Philip arrived.

Any remarriage would be unlikely in the extreme while the patriarch still has breath in his body.

But to those who dismiss the whole idea, it is worth noting that Andrew himself never has.

In 2009, he told an interviewer: “Do we have to be married? Well, let’s put it another way, I can neither confirm nor deny the possibility. We have two great children. We still look after them.”