The landscape painter JWM Turner was among the first of the great British artists to buy Winsor & Newton's silver tubes of coloured oil paints when the two men founded their art materials company nearly two centuries ago.
Ever since, it has been regarded as quintessentially British; founded in 1832, it was given Queen Victoria's seal of approval and holds a royal warrant, supplying paint to Prince Charles's household.
Now, in a most uncharacteristic move, the company is thinking of moving the manufacturing operation to a factory in France.
Nearly 200 employees at Winsor & Newton have been informed of a proposed move to Le Mans, which would mean the closure of its 69-year-old Wealdstone site, in Harrow, Middlesex, which specialises in making oil paints for some of Britain's leading galleries and artists.
The company's union is so horrified by the proposal that it is seeking the help of Prince Charles himself.
Peter Mead, senior steward of the union at Winsor & Newton, has written to Prince Charles, telling him of the proposed closure. "It is a very British company. We have tour groups coming to visit us... I wrote a letter to Prince Charles last week, and told him I was writing on behalf of the workforce at Harrow who were proud to display the royal warrant. I said any support would be gratefully received," said Mr Mead.
A statement from the company confirmed that following a global review, the ColArt Group, of which Winsor & Newton is a part, was considering the closure of the Wealdstone site – one of five factories in Britain and the main site for colour manufacturing – by the end of next year, to move to an existing site in Le Mans.
"ColArt has been under increasing pressure to become a leaner, more efficient operation," the statement said:
Neil Robson, the managing director of ColArt, added: "Wealdstone's physical location, in the heart of a residential area, makes it difficult to absorb additional capacity."
But Mr Mead said there were potential relocation sites closer to home.
A spokesman for Winsor & Newton said options would be discussed with staff during a 90-day consultation.
Richard Peck, secretary of the Royal Warrant Holder's Association, said warrants were reviewed on a five yearly basis and were not withdrawn automatically if a company moved abroad.
"The line that is taken is that if it's done for commerical and economical reasons, that is one thing. If it's regarded as being unethical in any way, it should be looked at more closely," he said.