Things then went downhill when British socialite and food critic Giles Coren tweeted: "Yes. it is an affair. i haven't read thee piece but i know about the affair. everyone knows about the affair, darling. even us jews. (although admittedly i'm quite a posh jew – if such a thing exists."
The Times food critic, however, has a reputation for stirring the pot (no pun intended), and quickly deleted the tweet. The accusations themselves have also been denied by many royal experts over the years.
In April this year, royal expert Andrew Morton assured New Idea that the "toxic story" was "false" and, although William and Kate "consider(ed) taking legal action", they ultimately "decided to ignore the chatter".
“William and Kate came out stronger than ever, the couple realising if any proof were needed, that this was the price of a life spent in the public eye." Andrew Morton told us.
So who is the woman once alleged to be William's mistress? Scroll on for everything we know about Rose Hanbury.
Marchioness Rose Hanbury was born on March 15th, 1984, making her 37 years old. She is married to David Rocksavage, the 7th Marquess of Cholmondeley.
The pair wed in 2009 at Chelsea Town Hall and, according to a report from Hello!, it was a whirlwind engagement, indeed.
"In June 2009 the couple announced their engagement, the next day it was revealed they were expecting and just a day later they tied the knot." the publication revealed.
Rose and David share three children together, twin boys Alexander and Oliver, as well as a daughter named Iris, and live at the Houghton Hall estate in Norfolk, which happens to be right around the corner from Kate and Will's country home, Anmer Hall.
The 37-year-old mother-of-three is constantly capturing stunning photos of the estate's gardens and sculptures which she then shares to her personal Instagram account, as well as a special one she made just for Houghton Hall.
Rose's ties to the royals run deep within her blood, starting with her grandmother - Lady Elizabeth Lambart - who was one of The Queen's bridesmaids when she wed Prince Philip.
While the brunette once worked as a model, she and Kate apparently grew close through their charity work with East Anglia's Children Hospice.
Despite the cheating rumours that sent shockwaves around the world back in 2019, both women remain married to their respective partners and seem happier than ever.