King Charles and Queen Camilla are "Deeply Competitive" Over this Unusual Hobby

Queen Camilla's son, Tom Barker Bowles, is revealing the secrets behind some of the most decadent royal recipes in his new book, Cooking with The Crown.

But along with sharing the Queen Mother's famous Gin and Dubonnet cocktail and his mother's simple porridge recipe, Parker Bowles reveals that his mom and stepfather, King Charles, have a surprising and passionately shared hobby.

Apparently, the two enjoy mushroom foraging and are "deeply competitive about their hauls," the food writer writes.

In the book, as reported by the Daily Mail, Barker Bowles says mushrooms are "somewhat of an obsession" for King Charles and Queen Camilla — the pair even try to out-forage each other.

According to Barker Bowles, the monarch relied on his long-time love of foraging and mushroom hunting after his mother, the late Queen Elizabeth, passed away at the age of 96.

On the day his mother died, then-Prince Charles "spent an hour at her bedside at Balmoral and then went to nearby Birkhall to gather mushrooms alone," the Daily Beast reports.

It was during his return drive from picking mushrooms that he received a phone call alerting him that his mother had passed and that he was officially the King of England.

In the book, Queen Camilla's son also reveals the differences in eating habits between the two royals, as well as how dedicated King Charles is to healthy, clean, farm-to-table eating.

"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," Bowles writes, going on to describe the monarch as "a true food hero."

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

In addition to the monarch's dedication to sustainability — which includes a pantry filled with "game, beef and lamb" as well as fruits and seasonal vegetables like "peas, strawberries, raspberries and chard" — Queen Camilla's son says that King Charles skips lunch, and instead of eating in the middle of the day enjoys a serious (but somehow still relaxed) afternoon tea.

"Tea however is a serious, though very relaxed meal, wherever it may be," he reveals in his new book. "While dinners, away from the official pomp and circumstance, are very laid back indeed."