The Duchess - otherwise known as Ann Fortune Fitzroy - served the royal household as Mistress of the Robes for Her Majesty’s entire reign to date.
In 1980, the Duchess was given the prestigious Dame Grand Cross of the Royal Victorian Order, which was an award made personally by the Queen for services to the monarch.
The Queen was also made godmother to Fitzroy’s second daughter in 1954.
Fitzroy had five children with her husband, the 11th Duke of Grafton Hugh Fitzroy, in 1946.
In her role at Mistress of the Robes, the Duchess was in charge of managing the ladies-in-waiting, and was on duty for the majority of important royal events, such as state visits.
Her death follows that of the Queen’s husband, the Duke of Edinburgh, who passed away in April at the age of 99.
Speaking a few days after his passing at a church service, Prince Andrew likened the death of his father to losing a “grandfather of the nation”.
The Duke said: “The Queen as you would expect is an incredibly stoic person. She described his passing as a miracle and she’s contemplating, I think is the way that I would put it.
“She described it as having left a huge void in her life but we, the family, the ones that are close, are rallying round to make sure that we’re there to support her.”