The exotic island is known to be a favourite holiday spot of the Duchess, who her parents there in 2008.
But the luxurious lifestyle (seemingly on the Crown's dime) has landed Kate in hot water, more than once.
Royal author Katie Nicholl detailed in her biography William and Harry that the Queen reached the end of her tether when it came to Kate's extravagant lifestyle.
“If she was not with William at Balmoral then the couple were skiing or holidaying on Mustique.
“Kate was there so often the press dubbed her ‘Queen of Mustique’, a title that had previously belonged to Princess Margaret."
Ms Nicholl continues: “Britain was now in a recession and such frivolous displays of wealth were unpalatable to the Queen.
“Swanning from one five-star holiday resort to another is not the prerequisite for a young woman possibly destined to be Queen.”
Ms Nicholl went on to describe how Kate was "stung" by the Queen's comments, and made concerted efforts to change her ways, although she still hasn't given up Mustique!
