For the past year Kensington Palace staff have dedicated hours of their week to moderating, addressing and deleting a torrent of online abuse on their social media accounts.
The targets of these messages, some of which contain death threats and most of which are infused with a dark sexist and racist undertone, are the duchesses of Cambridge and Sussex.
Kate Middleton and Meghan Markle have become a source of near-mania obsession for fans, with a Kensington Palace source telling HELLO! Magazine that the most unsettling messages seem hellbent on pitting the two women against each other.
"The Palace has always monitored comments but it's a hugely time-consuming thing," the source told HELLO! "They can block certain words, but some of it is quite serious. Over the course of last year, with hundreds of thousands of comments, there were two or three that were violent threats. It follows a Kate vs. Meghan narrative and some of the worst stuff is between Kate fans and Meghan fans. Arguments about who looks more appropriate, for example."
It's why the magazine has launched an online campaign, calling for an end to the torrent of online abuse directed at the wives of the princes William and Harry. But it begs an even more important question: why are we so obsessed with the idea of princesses at war with each other in the first place?
To find the answer, you have to look at the previous generation. You have to look at the relationship between Diana and Fergie. Because the media and the public told the exact same narrative about them.
The similarities between Diana and Fergie, and Kate and Meghan are remarkable. Both pairs married the two most eligible bachelors in the UK of their era. Both pairs were similar in age. Early coverage of both pairs of women portrayed them as getting along famously. When Meghan, Harry, Kate and William first started public appearances together, the press dubbed them "the awesome foursome".
The same was true of Diana and Sarah Ferguson. The incumbent Duchess of York became a close friend of Diana's as soon as she became engaged to Prince Andrew. In her biography The Diana Chronicles, Tina Brown reports that Fergie and Diana would "burn up the telephone wires trading gossip and irreverent royal titbits they could share with no-one else".
Acquaintances from around the social circuit, it was their partnership in royal crime that cemented the pair's friendship. Soon, they were gadding about West London in cahoots, dressing up as policemen to gatecrash Prince Andrew's stag night at ritzy nightclub Annabel's in Mayfair or running amok in the grounds of the palace.
But it wasn't long before the media turned the sisters-in-law against each other. "The narrative of a catfight was too irresistible for the tabloids," Brown notes. As The Sun's editor Harry Arnold noted: "It became fat Fergie against wonderful Diana."
There was some truth to the rumours. Several commentators have noted the ways in which both women were jealous of the other: Fergie envied Diana's poise, elegance and sense of style, Diana longed to fit in to the royal family with as much ease as Fergie had. After all, it was Fergie and not Diana who was often invited to dine solo with the Queen when Prince Andrew was away, and Fergie who initially endeared herself to Prince Philip when she took up carriage driving, the Duke of Edinburgh's beloved pastime.
"I got terribly jealous and she got jealous of me," Diana told the biographer Andrew Morton. "I couldn't understand it, she was actually enjoying being where she was, whereas I was fighting to survive."
But still the media latched on to a frisson and turned it into a fire. "Royal row!" the headlines read. "The rift that wrecked Fergie and Di's friendship". Another tabloid talked of their "shock vendetta". Their relationship was described as "bitter".
"Is Fergie's fizz leaving Di flat?" Vanity Fairposed in 1987, just a year after Prince Andrew and Fergie were married (sound familiar?)
That we expect the two wives of a pair of brothers to be bosom buddies is absurd in the first place. These women may very well have absolutely nothing in common besides the family they married into. In the real world, you would never demand sisters-in-law to be best friends. Somehow, this is expected of Kate and Meghan or Fergie and Diana.
In the latter case, it was a bit of both: sometimes friends, sometimes jealous of one another. Their relationship was more complex than a sound bite or a tabloid headline. Though it was true the pair weren't speaking at the time of Diana's death, Fergie had been a constant pillar of support through Diana's divorce from Charles, having gone through a royal divorce of her own at that point.
"(Fergie) was a very, very useful friend to the Princess during the months before her divorce," Jane Parkinson, Diana's friend and media adviser, said in The Diana Chronicles. "If she hadn't had her house to go to (Diana) would have gone mad."
But still the media insisted on whipping up the sexist narrative of a "bitter" feud and a "catfight" between them, simply because it sold more newspapers.
The same is true of Meghan and Kate. Pitting them against each other is a way of underscoring the age-old narrative of competition between women in the public eye. It's not just the royal family that has to endure this, it's all famous women, from Hollywood celebrities (Angelina Jolie and Jennifer Aniston) to pop stars (Madonna and Lady Gaga) to the judges on reality TV series (Delta Goodrem and Jessie J on The Voice).
If there's more than one woman in a particular space they must automatically be locked in a battle with each other, competing for the top spot. Because that's what women are like, right?
Neither Meghan nor Kate seem particularly interested in giving any fuel to that narrative, and rightly so. Take the launch of this new anti-bullying social media campaign or their nonchalant walk to church side-by-side on Christmas Day as evidence of that.
But it doesn't matter if rumours of their feud have been greatly exaggerated, they will continue to swirl. Not because they're the truth, but because it's a case of history repeating itself.
As we learnt back in the days of Diana and Fergie, there's nothing the media loves more than a pair of warring princesses.
Telegraph: The science behind road trip fatigue and how to combat it.