Queen Elizabeth II reportedly has one weird royal rule that Princess Diana struggled to live by.

Sir William Heseltine, one of Queen Elizabeth II’s former private secretaries, revealed that the late Princess of Wales felt that long evenings as agonizing.

“There’d be an hour or so in the sitting room of everyone sitting around making conversation and nobody felt it right to go to bed before the Queen did. And Diana was driven to such extremes that she’d excuse herself and go to bed, going to bed before the Queen,” he said (via Express).

Heseltine’s anecdote was echoed by Robert Jobson, the author of “Charles at 70.” He told Daily Mail that Princess Diana always wanted to get her way, especially when attending official engagements at night.

In 1988, they were scheduled to attend a state banquet held in honor of King Olav V of Norway. Princess Diana wanted to leave Kensington Palace already, but Prince Charles told his wife that they can’t go just yet.

“It may sound a little absurd but state banquets are where the business of royalty becomes very serious indeed. Diana did not quite see it like that. As far as she was concerned, a state banquet was just an irritation,” Jobson wrote in his book.

Ken Wharfe, Princess Diana’s former security, also witnessed the sore mood of Princess Diana at that time. He said that his former boss was tutting loudly and tapping her feet because Prince Charles didn’t follow what she asked him to do.

At one point, Princess Diana asked Wharfe if she could leave the banquet early, and he said that she couldn’t.

“Ken, I know all about their bloody orders… I want to go now,” the Princess of Wales said (via Daily Mail).

In order to stop Princess Diana from throwing a fit, Prince Charles decided to down a glass martini to calm his nerves.

“Diana, you know the system. We have to go at the set time so that we arrive just before Her Majesty,” Prince Charles told Princess Diana.