Slugs are killed by natural predators rather than pellets, rare breeds of pigs are kept to protect gene diversity, while head gardener David Howard has begun his preparations for global warming with a banana tree among the newer additions.

Charles, whose hobbies include the English rural craft of hedge-laying, is a vocal opponent of genetically modified crops and decided to convert his nearby Duchy Home Farm to organic methods around 20 years ago.

Organic farming was once derided as "knobbly vegetables for the neurotic" and "all muck and magic" but is now becoming more mainstream in England with sales soaring and Britain's major food retailers flaunting their green credentials.

The Soil Association, Britain's leading organic group, uses visits to Charles home and his nearby Duchy Home Farm to tell its story as its seeks to tap into a growing desire among consumers to know more about how their food is produced.

Terry Leahy, chief executive of Britain's largest supermarket chain Tesco, is among those who have taken the tour. Tesco has reported sales of organic food at its stores rose about 40 percent last year.

FARM VISITS

Soil Association Director Patrick Holden said the group saw farm visits as key as it seeks to promote a method of farming which shuns chemical fertilisers and promotes homeopathic cures for livestock.

London-born Holden said during a visit to Highgrove this week that his love of farming began with a visit aged five to a dairy farm in Essex. He now has an organic farm in west Wales.

Children from inner-city London boroughs are touring farms under a programme funded by Britain's national lottery.

"These children have absolutely no idea how food is produced," Holden said.

The programme also provides training for school cooks.

"The number one lesson that school cooks appreciated was how to peel an onion," said Soil Association policy director Peter Melchett, a strong supporter of the campaign to improve school meals launched by celebrity chef Jamie Oliver.

Highgrove House and the Duchy home farm are located near Tetbury in England's picturesque Cotswolds.

They were acquired in 1980 from Maurice Macmillan, son of former Tory Prime Minister Harold Macmillan, the year before Charles married the late Princess Diana.

The farm's livestock include Tamworth Pigs, among the oldest breeds which is thought to have descended from wild boars, as well as sheep and cattle.