Sarah Ferguson may have been a bad influence on Princess Diana, according to a royal expert.

While speaking with Daily Mail, royal biographer Sarah Bradford also said that the Princess of Wales was actually wary of the Duchess of York. But this didn’t stop them from engaging in mischievous antics. Bradford also said that Ferguson was a bad influence on the late royal because their mischievous activities wouldn’t have happened if not for her.

“I’ve not been a fan of Fergie’s and none of this would have occurred without Fergie’s bad influence. A member of the staff said Fergie had her own agenda and used to get Diana into trouble and then disappear,” she said.

Michael Cole, a former royal correspondent for the BBC, echoed Bradford’s statement by saying that Ferguson was always interested in causing mischief for Prince William and Prince Harry’s mom. On several occasions, she also left Princess Diana feeling embarrassed.

“Although they did fall out from time to time and were in and out of favor with the press, Princess Diana and the Duchess of York were friends from way back. Fergie was always up for any devilment that occurred to Diana, like livening up an afternoon at Royal Ascot by poking the royal equerry Major Hugh Lindsay in the back with the parasols when they spotted him walking along to the paddock,” he said.

Meanwhile, Princess Diana and Ferguson’s friendship was short-lived. Before their respective divorces, the two female royals had a falling out. A close friend of the royal family previously told Vanity Fair that the Princess of Wales couldn’t help but make comparisons between her and Ferguson.

Princess Diana didn’t also like the fact that Ferguson received all the perks of a royal but without the real stresses and strains that she had to go through herself. After all, she married the heir to the throne, Prince Charles, and Ferguson married Prince Andrew, who will never be King.

Princess Diana and Sarah Ferguson
Princess Diana was jealous of Sarah Ferguson because she knew how to win the hearts of the royal family. Pictured: Prince Andrew, Ferguson, Lord Linley, Prince Edward, Prince Charles, Princess Diana, Queen Elizabeth II and Queen Mother outside her London Clarence House residence on Aug. 4, 1989. Getty Images/Johnny Eggitt