More than 17 years after her death, Princess Diana remains one of the most recognizable beauty icons icons of the 20th century.

But when make-up artist Mary Greenwell first met the young royal, she was making the classic beauty mistake of using blue eyeliner, she told Stylist magazine.

"Blue eyes should never wear blue pencil or shadow" the make-up artist explained to the fresh-faced newlywed. "From that moment on, she was open-minded about trying new looks and colors.

had a long history working with the "People's Princess" as Diana was known since her 1991 photo shoot for Vogue UK (which was shot by famed photographer Patrick Demarchelier).

"She was just coming into her own when we first met and had just married Prince Charles," Mary told Stylist magazine.

"Her marriage seemed solid and she was just the most divine, sweet, kind lady," she continued. "It was a huge privileged to work with our then future queen."

One of Mary's first pieces of beauty wisdom for the young royal was to cease applying blue eyeliner.

"Diana was always very open and willing with her style. I think as soon as we worked together she realized the power of hair and make-up, and that is something that should never be underestimated. By anyone."

In addition to her beautiful blue eyes, another part of Diana's beauty legacy was her flawless skin. "Diana was pure magic and she had the most incredible skin," Mary divulged, "which frankly at the end of the day also can come down to family genes."

The royal stylist also revealed that "Diana was very sensible when it came to her skin, she would always make sure she took her make-up off at the end of the day and make sure she had a clean face before applying make-up."

According to Mary, Diana also understood the concept of "everything in moderation."

"She cut back on drinking so her skin was 100 percent. Women today need to take care of themselves the same way," Mary advised. "If you smoke, drink or do anything to excess, you will destroy your most important beauty asset – your skin."

Diana's skin was the perfect canvas on which Mary implemented an easy five-step beauty routine: "We always started with a moisturizer, a foundation to suit her skin tone exactly and then used a concealer to lift the eye area. Mascara – which is a gift of all gifts – and lip color to suit her mood that day.

"I always taught her to make sure when applying mascara by herself that she covered the roots of the lashes too!"

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