King Charles and Queen Camilla have a unique competitive hobby.

Camilla's son, Tom Parker Bowles, has revealed in his new book Cooking with The Crown, that King and Queen enjoy "mushroom foraging."

As quoted by Marie Claire, King and Queen's hobby is "somewhat of an obsession" for them and they are "deeply competitive about their hauls," often trying to out-forge each other during their outdoor adventures.

This hobby has reportedly provided comfort to King Charles, especially following the passing of his mother, Queen Elizabeth II.

On the day of her death, he spent time at her bedside and then went to gather mushrooms alone at Birkhall, a practice that has become a cherished escape for him.

"There is no man who knows more about food and farming, from the best of British cheeses, through rare breeds of sheep and cow, to heritage varieties of plum, apple and pear, than the King," the cookbook author wrote.

He added, "He very much practices what he preaches. The King has long talked about the importance of sustainable ­agriculture, and there is no waste at his table."

Moreover, he revealed that King Charles skips lunch and enjoys a serious afternoon tea instead.