image copyrightDavid Rolfee / The Aspinall Foundationimage captionThe breeding herd, including three calves, currently live in an enclosure at an animal park
An animal charity is planning to fly 13 elephants to Africa to rewild them in what it claims is a "world first".
The breeding herd would be flown to southern Kenya from the Howletts Wild Animal Park in Kent in bespoke crates.
The park is run by animal conservation group The Aspinall Foundation, which employs the prime minister's wife, Carrie Johnson.
Foundation chairman Damian Aspinall said: "It's unquestionably the biggest task we have undertaken."
The herd – which includes three calves – live in an enclosure at the park near Canterbury.
image copyrightThe Aspinall Foundationimage captionThe Foundation said crates had been specially made in South Africa for the journey
Mr Aspinall said: "As happy as they are in Kent, they don't belong here."
He told BBC Radio Kent: "Elephants don't do well in captivity. Hardly any are born. Females live to about half their natural life.
"Over half the elephants in captivity are obese. They suffer foot problems, skin problems, mental distress."
Mr Aspinall admitted the project, which he said was a "world first", had "big risks".
But he said: "We are trying to do everything to mitigate discomfort for these animals."
image copyrightThe Aspinall Foundationimage captionIt is hoped the elephants would settle in their new home within about 12 months
The herd, which weighs 25 tonnes, will travel in bespoke crates with veterinary support, he explained.
"Once they have got used to walking in and out of the crates, the hope is to get them get them onto lorries, and onto a direct flight to Africa."
Mr Aspinall said it could take up to a year after arriving before the animals are properly settled.
Two different sites in Kenya are currently under consideration for the project, which the charity says would be the first time a herd of elephants has been rewilded anywhere in the world.
Mr Aspinall added: "Once they get out there, they are going to be so happy, wandering about, meeting other wild elephants, breeding.
"I think we would have done something good in the world if we can achieve this."
Boris Johnson's wife is head of communications at The Aspinall Foundation.
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