We've known about the feud between Meghan Markle and Kate Middleton for so long that it's hard to remember a time when the two women appearedf to be getting along.
But to this day, insiders disagree on everything from the cause of the rift to its severity.
Some say the duchesses never hit it off from the very start.
Others claim they were perfectly civil to one another until a fight over a pair of tights at Meghan's wedding touched off a battle royale.
And while some claim that Meghan and Kate are simply stand-offish with one another, others insist that the two royal in-laws are bitter enemies.
Into that latter camp falls body language expert Judi James, who recently informed UK tabloid The Sun that Kate is so frightened of Meghan that she adopts a "fight or flight" stance when she's in the presence of Prince Harry's bride.
Of particular interest to James is a photo of the entire royal family at the christening of Meghan and Harry's son, Archie (below).
James says that the photo typifies the panic mode response that Meghan seems to bring about in Kate.
"With a very relaxed and jolly-looking Camilla down one end of this pose, Kate sits at the other looking oddly self-diminished and prim, with her arms pulled into her torso and a part-smile on her face," James tells The Sun, as reported by The Mirror.
"Given all the rift rumours the rather 'ready to flee' tension in her pose could be seen as awkwardness but it could also show a desire to lower her own status signals and not upstage the happy couple."
William, meanwhile, seems similarly tense, having adopted what James describes as "a self-protective barrier pose."
James is one of several experts whose insights appear in the new book Battle of the Brothers by royal expert Robert Lacey.
Lacey's is one of two recent bestsellers about the bad blood between the Cambridges and the Sussexes.
(The other, Finding Freedom, takes a much more favorable view of Meghan and Harry.)
Lacey points out that the day of Archie's christening would have been a particularly tense one for Will and Kate.
That's because Meghan and Harry refused to identify Archie's godparents, who would play the important role of "secret sponsors" to the newest member of the royal family.
"'Secret sponsor' has a dodgy sound to it. And it is an ingredient of Britain’s representative monarchy that the people should have the right to know who is giving moral guidance to their possible future king or queen," Lacey writes.
"‘Friends’ of William suggested that the future king, only five places clear of Archie in the order of succession, could not comprehend how such a basic matter of constitutional principle had been misunderstood," he continues.
"How could any new Windsor royal be christened in a meaningful sense without the newcomer’s sponsors being known, if not present?" he adds.
"What does such bizarre and paranoid behaviour indicate about the parents involved? One thing we may conclude is that Harry and Meghan had developed an exaggerated idea of their own importance."
Yes, Lacey says that for Will, Kate, and other important members of the royal family, the christening confirmed that WIll and Kate had allowed their narcissicm to run away with them.
"The months since their marriage had demonstrated that the couple share a common character flaw — they both have a tendency to cascade downwards from their peaks of generous self-confidence into miserable moments of self-pitying victimhood," he writes.
To this day, the identity of Archie's godparents remains a mystery.
But one thing that's seeming less mysterious every day is the extent of Kate and Meghan's mutual disdain!