And during his time away he received a 'cruel' letter from Camilla. She wrote to Charles to tell him that she had accepted a wedding proposal from Andrew Parker Bowles, a Guards officer who had been her on-off boyfriend since the late 1960s.

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.

Queen Camilla is "deeply competitive" with King Charles, according to her son Tom Parker Bowles, amid the couple's constant battle. King Charles is a keen champion of the environment, wildlife and the outdoors.

King Charles and Queen Camilla have an unusual hobby in common that they are said to become "competitive" over.

The little-known fact was revealed by Camilla's son, Tom Parker Bowles, who said King Charles and his mother were 'deeply competitive' about one unexpected hobby

Queen Camilla's son Tom Parker Bowles spoke about King Charles' health amid his cancer treatment in a new interview with British Vogue.