Queen Elizabeth reportedly has a simple trick that lets her kitchen staff know if she has guests coming over for a meal.

In “Secrets of the Royal Kitchen,” Her Majesty’s former royal chef said that he and his team give Her Majesty a menu book that includes menus good for three days.

After the Queen returns the menu book to McGrady, they would see all of the dishes that she put a line through. These are the dishes that she doesn’t want to eat.

“If she’s out for dinner she’ll put a line through the page, and if she has a guest coming, she’ll put two or three so we know she is entertaining,” he said.

And royal correspondent Emily Andrews also said that palace staff chooses the Queen’s plate randomly when she is at parties and other gatherings to ensure that she won’t be poisoned.

“After everything is plated up, a page chooses at random one of the plates to be served to Her Majesty. So, if anyone did want to poison the monarch, they’d have to poison the whole lot,” she said.

In the past, royal experts and palace staff have already shared some of the secrets in the royal kitchen. For instance, Andrew said that the monarch is the first person to sit down during dinners. She is also the first person who eats at gatherings.

And when the Queen is finished eating, everyone else should stop eating too. This rule forced courtiers to eat their food quickly just to make sure that they are done before Her Majesty finishes.

McGrady also said that he never serves anything with garlic when the Queen is around because she doesn’t like its taste. The mom of four is not a fan of onions either.

And since the 93-year-old royal is not very adventurous when it comes to food, her kitchen staff usually serves her tried and tested dishes that she previously enjoyed.

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