The Prince of Wales has become one of Britain's most successful living artists, selling prints of his paintings for millions of pounds.
An analysis of sales of limited edition lithographs conducted by Clarence House and released to The Telegraph shows that the Prince has earned £2 million ($4.4 million) since 1997 from sales of copies of his watercolour paintings through the shop at his family residence, Highgrove House. All the money raised goes to the The Prince of Wales' Charitable Foundation, which awards grants to a wide range of good causes.
But the total sales are even larger. An art dealer who previously handled sales of the Prince's lithographs estimates they raised at least £4 million, bringing the total to more than £6 million.
The lithographs on display in the Highgrove shop carry a price tag of £2,500, but the Belgravia Gallery, which previously handled the sales, is currently offering limited edition prints for as much as £15,000.
The income places the Prince among an elite band of living artists. The most recent survey showed fine artists earn on average £10,000 a year. By contrast, the Prince has, when his earnings are averaged out, made in the region of £200,000 a year from art sales over the past 25 years.
According to Clarence House, the Prince paints "in the open air, often finishing a picture in one go".
His favourite locations include the Queen's estate at Balmoral and Sandringham House. "Sometimes the Prince paints during his skiing holidays, and during overseas tours when possible," said a spokesman.
The Prince sees his watercolours as part of his legacy. "We walk away and shuffle off our mortal coil, but these things live on," he said in a television documentary in 2013.
The Prince only paints with watercolours and never sells the originals. He began making money from his hobby when he was approached in 1989 by Anna Hunter, owner of the Belgravia Gallery in central London. "I saw his work as a water colourist in a Sunday newspaper magazine article in 1989," said Mrs Hunter.
"Until then I had no idea he was an artist. I wrote him a letter suggesting that if his works were made into signed lithographs, they could be sold to raise money for his charitable foundation.
"I didn't hear anything for ages and then just before Christmas 1989 his private secretary called me and said he was very interested and could we meet." Subsequently, and in conjunction with a print maker, Stanley Jones, Prince Charles released a series of limited edition lithographs with runs of either 295 or 100. They included views of Windsor Castle, Balmoral, and a scene of Hong Kong from the Royal Yacht Britannia.
In all, the Prince produced 16 lithographs during the commercial tie-in with the Belgravia Gallery. "We did a tot up about eight years ago and reckoned we had raised £ 4 million then," said Mrs Hunter. "It was a really lovely project. The originals are mostly at Highgrove. I think these are really charming works of art in the English watercolour tradition and they are a really good reflection of the talent that lies within the Royal family for art."
The Prince's latest series of three lithographs, each with a run of 100, were released in 2014. One has already sold out, raising in the region of £250,000. Not bad for an amateur who does a bit of painting on the side.