When Diana and Charles headed to the Klosters in 1986, the pair were spotted skiing down a nursery slope, decked out in full ski gear.
Due to their desire to keep the visit private, it was arranged that the paparazzi would be able to snap photos of the royal couple at a secret location upon their request. The press happily snapped photos as the pair gracefully glided down the slopes.
The attention on Diana was quickly over-shadowed by her sister-in-law Sarah Ferguson who was also visiting the Klosters for a ski holiday. At the time, Sarah was dating Prince Andrew but she chose to go on the trip alone due to Andrew being busy serving with the Royal Navy.
Sarah's unexpected appearance cause Charles' truce with the press to be threatened as the paparazzi went into a frenzy to take photos of all the royals skiing together. This violated the pledge set up with the media who had promised to leave Charles and Diana alone to enjoy their trip.
The two friends even pretended to fight during a press opportunity. However, Charles labelled their actions childish and criticised them for it, reported Express.
The following year, Sarah and Diana returned to the Swiss village with both Charles and Prince Andrew in attendance.
Sarah was introduced to Andrew - who is Charles' brother - by Diana, which effectively kindled the start of their romance.
Once Sarah married into the Royal Family, her bond with Diana strengthened. However, their friendship quickly soured once Sarah obtained her pilots license and took up carriage ridding. Sarah's actions drew praise from the Queen and Prince Phillip. Charles often compared Sarah to his wife and once told Diana, "I wish you would be like Fergie - all jolly."
The two friend's did not stay mad at each other for long and rekindled their friendship in 1991, a year prior to them both separating their husbands.
Five years later, their friendship once again crumbled and it was suspected that the cause of the fallout was due to way Sarah had described Diana in her autobiography which was released in November 1996.
The two ladies never got the chance to reconcile as Diana sadly passed away in a car crash in Paris, 1997.