Prince Charles and Princess Diana were each 5'5" tall, and because of Prince Charles' ego, Diana refused to wear shoes over 2 inches during their marriage, a new book claims.

In this summer's new book, "The Lady Di Lookbook: What Diana Was Trying to Tell Us Through Her Clothes (opens in new tab)," Eloise Moran explores the fashion icon's style Delving into the transition, she writes in Insider, "For years, Diana never wore shoes taller than two inches out of respect for her husband's ego. (It attracted 118,000 followers, who zoomed in specifically on Diana's looks post-divorce.)

During their marriage, however, Diana's heels were short. Moran specifically looks at and dissects the attire worn by the late Princess Charles to pick up Prince Charles from Cirencester Hospital after he broke his arm in 1990.

"Diana styled an unbuttoned chambray shirt over a casual white T-shirt and paired it with a floral knee-length skirt and coordinated, but not quite matching, flat shoes," she wrote, calling it a "pre-divorce revenge look."

Diana's "look" was "a very different one.

As Diana's style evolved through her years in the spotlight, from her marriage to the Prince of Wales in 1981 until his untimely death in 1997, "as her estranged royal confidence grew, so did her heels," Moran Moran writes of Diana. Jimmy Choo recalls that at the beginning of their seven-year friendship, Diana always ordered flat shoes. First 2 inches, then 3 inches, then 3.5 inches, then 3.4 inches. It just kept going up and up," Chou said.

Chou was a close associate of Diana's and she was a "big fan" of his 1990s designs, Moran wrote.

"He often joined her at Kensington Palace, where he ransacked samples and co-developed her next pair," she wrote.

Tragically, Chu was even prepared to deliver a pair of pumps to Diana upon her return from a trip to Paris in August 1997.

"She tragically never received it, and Jimmy kept it in his personal collection in memory of Diana, his friend and best customer," Moran wrote.