Prince Charles and Duchess Camilla never eat garlic.

Prince Charles and Camilla

Prince Charles and Camilla

The Duchess of Cornwall revealed during a special episode of 'MasterChef Australia' that the one ingredient the British royals should never eat is the pungent vegetable because they spend so much time chatting with the public they can't afford to have bad breath.

Camilla said: "I hate to say this, but garlic. Garlic is a no-no. It's always so - you just have to lay off the garlic."

The 70-year-old royal also revealed what foods are her husband Charles' favourites, spilling that the 69-year-old heir to the throne has a huge appetite for cheese.

She added: "He loves local cheeses; he's a huge cheese fan. Anything to do with cheese, he'll love ... Anything with eggs, with a bit of local vegetables of some kind, he'd love that. You'd definitely see a smile."

The contestants of the show were tasked with cooking a meal fit for the royal; Camilla was particularly keen on one meal, telling one contestant: "I'm particularly partial about local ingredients. And that's what makes it so fascinating is the diversity."

Camilla's son Tom Parker Bowles is a food critic and chef and has written five cookbooks.

The 43-year-old foodie has opened up about the royal menu before and praised his mother for her own culinary skills in the kitchen.

Explaining why he doesn't cook for his mother and stepfather, Tom -whose father is Camilla's ex-husband Andrew Parker Bowles - said: "She's amazing at scrambled eggs and usually I leave her to do, whatever it is, roast chicken or scrambled eggs, I leave her to do it. I usually wouldn't cook for him (Prince Charles) most my food has chilli in it or endless spices and no, no I wouldn't do it.

"They have very, very good cooks, proper chefs, so why would they want me to do it? I like chillies and I like onions and garlic and as she's got older garlic and chilies are especially a no-no and you can't go stinking of garlic when you are shaking a few hands the next day."