Sarah Ferguson was reportedly "no real competition" to Princess Diana.

The late Princess of Wales and the Duchess of York were very close. In fact, many believe that they were best friends. According to journalist Sue Arnold, there's a reason why the People's Princess didn't mind being compared to Ferguson.

"Fergie, as she's known to her friends, is a jolly nice girl, supremely suited to the role of second-string daughter-in-law, horsey, bouncy, with an unthreatening I.Q," Arnold said (via Express). "Diana chose well, for though Sarah is pretty, she's no real competition. In looks and attitude, she is the perfect foil to the charismatic Diana."

Princess Diana and Ferguson had been friends even before they married Prince Charles and Prince Andre, respectively. The two were fourth cousins. In fact, Princess Diana invited Ferguson to her royal wedding to the Prince of Wales and provided the latter with fabric for the event. She was also the one who introduced Ferguson to the Duke of York.

However, there were reports claiming that their friendship had gone complicated when people started to compare them. According to Andrew Morton, there was a time when Prince Charles reportedly told Princess Diana, "I wish you would be like Fergie - all jolly."

However, their friendship ended when Ferguson reportedly made a confession in her 1996 book "My Story." In the publication, she wrote that she got a verruca after borrowing Princess Diana's shoes. The late Princess of Wales was reportedly upset that she was even mentioned in the book when Ferguson already promised to not talk about her.

In her 2011 book "Finding Sarah," Ferguson wrote about Princess Diana again. She recalled how Prince William and Prince Harry's mom made her laugh and her heartbreak that they didn't speak before her accident.

"Diana was one of the quickest wits I knew; nobody made me laugh like she did," Ferguson wrote. "We took vacations together with our children. Sadly, at the end [of the Princess's life] we hadn't spoken for a year, although I never knew the reason, except that once Diana got something in her head it stuck there for a while."

Ferguson reportedly tried to reach out to Princess Diana, but all of her efforts were in vain. They were not in speaking terms until the latter died in a car crash in 1997.