The Duchess of Cornwall has lost a long-running planning battle to thwart permission for her next door neighbour's 'granny' flat.

Camilla, 71, kept her former home, the Grade II-listed Rey Mill House after she married Prince Charles in 2005. The royal locked horns with neighbour Phil Clayton when he applied to demolish an outbuilding next to his house and build a flat for his elderly mother.

The Duchess objected to his plans three times, via letters from the head of Charles’s Highgrove estate written on HRH-headed notepaper. Despite her objections, on December 12 Wiltshire Council planners approved the plans for the flat which will be 60m from the Duchess' property, in Reybridge, near Lacock. It comes after the pair also clashed last year over other renovations at his home, The Old Mill, which shares a private lane with the Duchess' property.

Outlining the granny flat decision, council officer Alistair Cunningham, said "This distance [60m] combined with the simple design of the outbuilding, means it is not considered that there would be any harm to the setting of Rey Mill House from the proposals."

Camilla bought the property in 1986 for £850,000 following her divorce from Richard Parker Bowles. Mr Clayton bought his nearby £675,000 home in 2017 and initially focused on renovations to the main house.

The businessman submitted plans which included increasing the size of the bedrooms, lounge and dining room, and building a separate extension with a sun room. The Duchess and other locals objected over flooding concerns and the plans were withdrawn in March last year, with revised proposals submitted a month later.

Camilla did not object to the revised application and it was approved in July. But at the same time, Mr Clayton submitted plans to demolish an outbuilding and build a granny flat for his mother. Again, Prince Charles' Highgrove estate manager Charlie Craven objected on behalf of Camilla.

In a letter to the council's planning team, he said: "I believe it will have a negative effect on the flow of water from the river during periods of flooding.

"The river has flooded numerous times.

"Anything that hinders or alters the natural flow of the river to the detriment of other properties is clearly unacceptable," he wrote.

The council rejected the plans in July - claiming they did not address the potential impact of flooding - so he revised and resubmitted them a month later. Camilla and other neighbours again objected to the revised plans.

Mr Craven repeated flooding concerns in another letter, and others also wrote to the council to object - so Mr Clayton changed his submitted plans. He increased the size of the flat by 25 per cent and turned the angle of the building by 90 degrees which he said would reduce the risk of flooding.

The head of Charles’s Highgrove estate objected once more and said in a letter he was "encouraged" by some changes, but "perplexed" over the size increase.

Fellow neighbour James Campbell also wrote: "Our main concern is with flooding and we have experienced several major incidents since we came to live in Reybridge in 1993.

"The present owner of 'The Old Mill' has not experienced a serious flood of the Avon at Reybridge and so is presumably unaware of how quickly and dangerously the water rises and flows at such a time.

"Anything which could theoretically exacerbate the extent of flooding is of serious concern to us and indeed to our immediate neighbours."