Alterations will give the buildings "a new lease of life".

The Duchy of Cornwall had applied for an extension, conversion and new building at Llwynywormwood in Myddfai.

Six Carmarthenshire councillors opposed the application saying they had refused many similar requests due to strict rules on building in the countryside.

But 14 others backed the plans for the �1.2m former coach house and estate.

The Prince bought the 192-acre retreat earlier this year as a base for when he and the Duchess of Cornwall visit Wales.

Two families objected to the plans to refurbish the estate claiming they had been refused planning permission in similar circumstances.

Our proposals have high regard for the historic nature of the parkland and the buildings David Curtis

Councillor Tyssul Evans told the meeting in the past the planning committee had rejected "hundreds of similar applications" due to rules aimed at protecting the open countryside.

"We have been unable to help them - many of these people live and work in the countryside," he said.

"I do not see why it should be any different in this context."

The Duchy of Cornwall's application included a first-floor extension to the farmhouse, conversion of adjoining building and work on a dining room, reception/sitting room, kitchens and three bedrooms.

The more modern agricultural buildings to the west side of the courtyard would also be rebuilt as two, two-bedroom ancillary accommodation.

Charles and Camilla will use the building as a Welsh base

In addition, the modern agricultural buildings to the north west of the historic courtyard buildings would be demolished in favour of a thatched roof traditional building with a gravel car parking area.

David Curtis, representing the duchy, told the meeting: "Our proposals have high regard for the historic nature of the parkland and the buildings."

He said the alterations would provide a reception area to host guests, a conference facility and the additional accommodation would be for royal household staff with occasional holiday lets.

Moving that the application was approved councillor Bill Thomas admitted that the plans were "a departure" from the council's own development plan but said it would improve the look of the estate.

Llwynywormwood is a former coach house set in the grounds of a ruined mansion.

Overlooking an 18th Century country park, it includes 40 acres of woodland, a walled garden and the remains of a lake.