Jamie Oliver says the organic free range turkeys animal-friendly and taste-conscious Brits ate today were not necessarily the happiest or tastiest around – because the traditional festive birds fear open spaces.

The TV chef said turkeys are genetically programmed to feel vulnerable to prey without cover, and the best Christmas birds are ones that roam around in woods.

Oliver said leaving turkeys under the protection of a tree canopy is like “the Ritz” and produces very “delicious healthy” stress-free birds.

The cookbook author said he works with award-winning turkey producers KellyBronze making the “Ferrari” of beautiful-tasting turkeys bred in forest conditions.

Oliver, 48, said: “I am a turkey farmer. I did 3,500 turkeys this year.

“I work for a guy called Paul Kelly – KellyBronze (correct) – and we have those lovely rare breed turkeys.

“I’m one of his 23 farmers and they’re all bred in the woods, and it’s like the Ritz for turkeys – except until the last minute. They’re very delicious.

“The important thing is that free range organic is lovely, but what they love is dappled light and they love forests.

“Poultry doesn’t really like free range. They’re very scared, they’re always thinking they’re going to get eaten by an eagle or something.

“So when you get one from a wood then they’re really happy – they’re just very fit, healthy.

“They’re dealt with very beautifully and respectively. It’s like the Ferrari of turkeys.”

A study published five years ago by poultry consultant Edward Mailyan said turkeys are particularly susceptible to stress and its hormonal consequences.

He reported the steroid corticosterone rises, which effects other hormonal systems, such as the conversion of noradrenaline into adrenaline or the production of thyroid hormones.

Adrenaline then reduces lactic acid, which can make meat tougher and less tasty. The meat can also go bad quicker because the acid would help to slow the growth of spoilage bacteria.

The end result is a change to major metabolic processes with severe changes to carbohydrates, proteins and lipids break down, plus slower growth.

Kelly rears his own turkeys, but also takes some from other approved farmers like Oliver, who he supplies with feed and checks on conditions.

Paul Kelly’s Essex-based family business was started as Kelly’s Turkeys by his father Derek in 1971.

They were already winning awards for their high quality white turkeys when in the face of supermarket competition, and after Paul studies Poultry Science at university, he branched out into breeding the original bronze turkey that came from Mexico.

He travelled the country buying up the last flocks of pure bronze turkeys.

They received a huge boost after they were endorsed by Delia Smith in her past Christmas book.

She has said with “care and dedication” the company produces “the real thing..with all the character and flavour it was meant to have”.

The KellyBronze was the first ever turkey to receive three gold stars in the Great Taste Awards.

Paul said: “This is the best way to look after turkeys. When they hatch we put them into what we call brooding sheds under heaters and then by about five weeks of age they’re ready to be brought into the woodland.

“We’re the only ones in the country to be doing this. We come in the morning and they’ve stripped the nettles until they can’t reach anymore and it’s great to trample them down because then they’ll finish them off.

“They love it. They dust bath. They’ve got blackberries. They’ve got all the seasons eating soft fruits. That’s what makes them taste so great.

“Turkeys do get stressed about overhead prey. If a plane or drone goes overhead you see them run for cover. The breed of turkeys we have originated in Mexico where their main threat is birds of prey when they are younger. So they will naturally prefer cover and trees there.

“Plenty of work has been done on animal species that shows if an animal is stressed then the meat is tougher, although I don’t know of any that specifically concentrated solely on studying turkeys.”