Rivett, who worked with Diana for over seven years, opened up about Diana's exercise regimen in 2018.
"Every single session all the media were outside camped with their stepladders, and cameras and lenses and everything. For her she just found it so incredibly, 'why are they so interested in me when there are more important things to worry about in the world.’
"It wasn't her that asked for all this. I remember one of her strategies was that she was going to wear the same Virgin Active sweatshirt every single session," the London-based personal trainer told Yahoo's series The Royal Box.
The sweatshirt is accompanied by two letters of provenance from Rivett, with one reading, in part:
“This sweatshirt was given to HRH by Sir Richard Branson. It became the most worn top on her regular visits to the gym. She felt there were far more important issues to focus on in the world than her gym attire and therefore decided that wearing the famous Virgin sweatshirt to every session, would be a good way to stop the media frenzy.
"A few months before her untimely death she called me to say she had left a few sweatshirts for me. Amongst them, this one—which I have now decided to part with."
The Princess of Wales had a disciplined approach to building a strong exercise routine. Rivett described Diana as "incredibly dedicated" to her sessions. She integrated at least three 30-minute sessions of vigorous exercise each week. When possible, she began her day with a morning swim or attended to her children’s needs. If she had no time to swim, she’d fit in a bit of stretching before breakfast.
When it comes to Diana's daily diet, former Buckingham Palace chef Darren McGrady, who first served the Queen and the royal family before transferring to work for the Princess of Wales, shared some tidbits from his eleven years cooking for Diana.
McGrady worked for Diana after she split from Prince Charles in 1993. After publicly struggling with bulimia, Diana is credited with raising awareness about the eating disorder.
Her time with McGrady marked a positive turn in her lifestyle, the chef noted in his book Eating Royally: Recipes and Remembrances from a Palace Kitchen.
"She was entering a new stage in her life and taking better care of herself. Her years as a bulimia sufferer had ended and she was eating properly," he wrote. He also revealed to The Daily Mail that in her quest for healthy eating, she stayed far away from carbs and red meat."
She'd tell me: "You take care of the fats, I'll take care of the carbs at the gym.'"