Sara, who was formerly married to Camilla's son Tom Parker-Bowles, and who is the mother of Queen Camilla's grandchildren Lola, 16, and Freddy, 13, told The Times: "Camilla was really, really nervous. She wanted the people that she loved around her. [King Charles] wasn't nervous at all. But Camilla didn't ask for any of this.
"She's the human face of the royal family, because she's not part of it. You need those outsiders really," Sara added.
Tom's ex-wife also revealed that her son Freddy, who was part of Queen Camilla's team of page boys along with Prince George, also did a little wave that he "wasn't supposed to do," but was "awestruck" watching the flypast from the Buckingham Palace balcony.
At the time of the coronation, King Charles and Queen Camilla's former royal butler Grant Harrold also noticed the monarch's nerves, claiming he recognised the royal's mannerisms as "unquestionable nerves."
Grant, who butlered in Highgrove House for Charles and Camilla, revealed on behalf of Spin Genie: "You could see Camilla was nervous, there was no question about that. You could just tell her by her mannerisms, but I loved the fact that she was still smiling."
Grant added: "During the service, there were one or two moments where Camilla would look over and give Charles a smile and it looked like she wanted to have a giggle with him. That’s very much her, she’s fun and down-to-earth. And even though the day would have been very stressful and also emotional and nerve-wracking for her, I thought she handled it all very well."
Despite her seemingly nervous disposition, Queen Camilla was a vision of regality on the day, donning a magnificent ivory gown designed by Bruce Oldfield that took "six years to make."
Keeping her passions and loved ones close to her heart on the historic occasion, the Queen's beautiful dress was adorned with stunning embellishments that paid a subtle tribute to her family.
Oldfield embroidered the names of her children and grandchildren discretely near the bottom of her skirt, while the swathes of ivory fabric featured delicate garlands of abstract wildflowers from fields and hedgerows – daisy chains, forget-me-nots, celandine and scarlet pimpernel, representing The King and The Queen Consort’s affection for nature and the British countryside.