In showbiz terminology, the moment a wildly popular phenomenon suddenly begins to hit the down-slope is known as Jumping The Shark.
And 2012 may have seen the moment when Pippa Middleton, she of the heavenly derrière, went from Media Princess to Ugly Sister (in her public persona, at least).
In terms of profile, her now pregnant sister is sure to hog all of the headlines over the coming months. And that leaves Pippa, with her disastrous book and plummeting popularity, in a tough place.
Ms Middleton pocketed an advance worth just under €500,000 from publishers Penguin for her how-to party-planning book Celebrate.
However, it arrived to appalling reviews, public derision and poor (to be kind) sales, shifting just 2,000 copies in its first week on British bookshelves.
The 29-year-old sister of the Duchess of Cambridge suddenly found that more than two years of fawning press coverage had ended overnight. She was derided as a dim Sloane, trying to put one over on the gullible public and cash in on her sister's worldwide fame.
Even Jilly Cooper, the 75-year-old 'bonkbuster' author, who should know a thing or two about selling books, was moved to observe of Pippa's magnum opus, "It's terrible, isn't it?"
"The sales have been dreadful, and I hear that the people at Penguin are virtually slitting their wrists over it."
Ouch! Poor old Pippa might be spending this festive season nursing her wounds, with the help of some lovely turkey and mushroom vol-au-vents she's knocked up in minutes from leftovers.