Prince Charles may currently be in good standing with Queen Elizabeth II, but their mother-son relationship may not have always been so positive.

Last September, Express revealed that Charles once “embarrassed” the monarch by failing to attend a 1999 event planned by China’s then-president Jiang Zemin. According to the outlet, the Prince of Wales chose not to attend the state dinner due to his support of Tibet’s claim of independence from China.

At the time, the U.K. was trying to foster a positive trading relationship with China, therefore making the event important. And while the rest of the royals rolled out “the red carpet,” Charles was nowhere to be seen. It was later revealed that he had hosted a dinner party with now-wife Camilla, Duchess of Cornwall, the same evening instead. The royal’s absence was called “deliberate” by his former aide Mark Bolland.

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“There absolutely was an expectation that Charles would be there and the way that the royals arrive at these banquets, the Queen is the last to arrive, so Charles would have been sort of the second last to get out,” royal correspondent Richard Kay told Channel 4’s The Royal House of Windsor.

“And when the car came and it was the Queen getting out, then obviously we realized we had a big story here because the Prince of Wales wasn’t there.”

The outlet noted that Charles’ lack of appearance was immediately viewed as a “boycotting act” and deemed scandalous due to royals usually staying out of political matters. His actions, according to Kay, were also viewed as disrespectful towards the Queen.

“By not attending on this occasion, he was not only letting down the monarchy, he was embarrassing his mother,” he said, adding, “Buckingham Palace’s response was one of anger, so angry in fact that some of their senior officials briefed journalists about what they described as a 'petulant and selfish prince.’”

Queen Elizabeth II and Prince Charles
Queen Elizabeth II is photographed with Prince Charles at a reception to mark the 50th anniversary of the investiture of The Prince of Wales at Buckingham Palace in London on March 5, 2019. Getty Images/Dominic Lipinski