The Full Story Behind Princess Diana's Iconic HaircutDoug Mills/AP/Shutterstock

The late Princess Diana was renowned for her profound effect on the fashion world, but her most famous hairstyle almost never came to be.

Sam McKnight served as the hairstylist for a 1990 British Vogue photo shoot, but he didn’t know ahead of time who his client would be. It wasn’t until Princess Diana walked into the room that he realized he’d be working with royalty.

“She came bounding up the stairs in a studio in Hackney, this beautiful long-legged blonde, and immediately made us all feel totally at ease,” McKnight told TODAY. “She had an amazing way of disarming you and kind of getting rid of all the nerves, and laughing and making jokes.” Don’t miss these 20 rarely seen photos of Princess Diana.

McKnight decided to try something new with Diana’s hair, which at that point was close to shoulder-length and still had some classic ’80s volume. In his book, Hair by Sam McKnight, he explained how he did a bit of follicle manipulating magic, tucking her hair behind a tiara to fake a shorter ‘do.

The style looked stunning in the shoot, but it could have stayed a one-off look for the magazine—that is, if Diana hadn’t been so inspired by what she saw.

“As she was leaving, Diana asked what would I do to her hair if I had free reign,” McKnight writes. “I suggested cutting it short and she, to my surprise, agreed, and we did it there and then.”

The Full Story Behind Princess Diana's Iconic HaircutNews UK Ltd/Shutterstock

So, Princess Diana came in for a photo shoot and left with a sporty pixie cut—a dramatic change from her old style, which didn’t sneak by the press. Immediately, Diana’s new hairdo was all over the media, and shorter styles started trending. “It was quite astounding,” McKnight told TODAY. “I discovered the power that she had in the press. The manner of coverage was quite extraordinary.” Check out some more of Princess Diana’s most iconic fashion moments.

After the spontaneous quick snip, McKnight formed a working relationship with Diana. Whenever she was in London, he would swing by for a morning hair maintenance appointment and would sometimes swing by in the evening if the Princess had an event in the evening or even accompany her on humanitarian trips.

But it wasn’t just Diana who took a liking to McKnight’s stylings; William was a pretty big fan, too. “Sometimes her beloved boys would be there and I would cut their hair, too,” he writes. “I remember Prince William responded in glee when I put gel in his hair for the first time.”

Yep, a haircut that shaped a decade of style was done without an appointment. Check out these other 10 fascinating facts you never knew about Princess Diana.