Queen Elizabeth II has defied her own royal rule when she did a surprising but sweet gesture during one of her Buckingham Palace garden parties.

On Thursday, the Queen, 93, invited hundreds of guests over to her home for a garden party. And while mingling with the attendees, Her Majesty surprisingly broke her own protocol when she stopped and accepted a bouquet of flowers from one of her guests.

Laura-Ann Barr, a mother of two from Northern Ireland, was one of the few lucky guests to have spoken directly to Quen Elizabeth II and made sure she would be remembered by giving the monarch a sweet gift. Her mother, who came along with her, caught the rare moment of Queen Elizabeth accepting the flowers on camera, and Laura-Ann later shared the video on Instagram.

Barr told Hello! magazine that she decided to buy the bouquet at a flower shop at a train station despite being aware that guests didn't usually bring flowers to the palace garden party. She apparently just wanted to "give her all" for her "one chance of meeting the Queen."

Barr explained that she had been told by security at the royal tea tent entrance that Queen Elizabeth likely wouldn't accept her bouquet of flowers as it was against royal protocol. However, she still hoped that a lady-in-waiting would take the gift on Her Majesty's behalf.

Due to this, she was shocked when the Queen herself accepted her flowers, and Barr believes Her Majesty's staff was equally as surprised as her.

Queen Elizabeth II
The Queen smiles as she arrives before the Opening of the Flanders' Fields Memorial Garden at Wellington Barracks on November 6, 2014 in London, England. Getty Images/Stefan Wermuth-WPA Pool

Describing the moment as "surreal," Barr detailed what it was like meeting Queen Elizabeth at the garden party, explaining that the monarch was very warm and polite.

"[The Queen] was walking towards me and happened to look up and briefly made eye contact," Barr explained. "At that point, I curtsied and loudly said, 'Your Majesty I have some flowers for you.' It was deadly silent, everyone was watching her and all you could hear were camera shutters snapping!"

"She popped her umbrella in her other hand and put her hand out and approached me with a very charming smile and thanked me! I told her she looked beautiful in pink and she smiled again," she continued.

But while this was a rare moment, this wasn't exactly the only time Queen Elizabeth II broke royal protocol. During the 2009 G20 Summit in Buckingham Palace, the monarch put her arm around then-first lady Michelle Obama, a moment which was also captured in a video.

Back in 1998, the Queen also made a special exception for a young boy when she signed his soccer ball during her visit to Malaysia.