The couple bought the house for �300,000 in 1998

The 18th century Grade I mansion is being sold for more than �6m.

The magazine's editor Clive Aslet said it was chosen as a cover for a themed issue on property and estates.

He denied that any pressure had been exerted from the Royal camp and decided to make an exception to the magazine rule for a "beautiful house".

"There are certain sorts of things that turn our readers on and if we have a beautiful house on the cover, sales will go up.

"We have never, ever had a house on the market before. When I saw the advert, I thought 'this is the most beautiful house', so I waived the rule," he said.

The Country Life cover follows the news last month that the Princess is to make a television programme, documenting her efforts to sell Nether Lypiatt.

The Royal couple bought it in 1980 for around �300,000. They are now expected to live at their Kensington Palace apartments.