HE WAS one of the most influential designers of the 20th century, creating a style that became the epitome of Scottish art nouveau.
His trademark images adorn everything from calendars to tea mugs and examples of his original work - including chairs, tables and cutlery - are among the most collectable of any Scottish artist.
His architectural designs are equally renowned, with the famous School of Art building and the Willow Tea Rooms in Glasgow still visited by fans from around the world.
But a new exhibition of Charles Rennie Mackintosh's work opening in Edinburgh is set to lift the lid on a lesser known side of the artist. Organisers hope to display more than 40 watercolour paintings created by the artist in the last years of his life.
And there will also be a previously unseen collection of letters written to his wife which give a unique insight into his thoughts on his life and his painting.
Mackintosh painted 44 watercolours during a stay in the French village of Port Vendres, although the whereabouts of three are unknown. The 41 survivors have been tracked down following a two-year search by staff at the Dean Gallery.
Now they are set to be brought together again for the first time in over 70 years. And, as the exhibition approaches, the museum is still scouring private collections across the globe in a bid to secure missing paintings for the show.
The exhibition focuses on the last few years of Mackintosh's life, when he took a four-year extended holiday in the village near the Spanish border.
Disillusioned with his architectural work in Scotland, Mackintosh went abroad to consider his future. While there, he threw himself into watercolour painting, something which had long been a hobby but to which he had never truly devoted himself.
Over the next four years, he painted 44 watercolours and was planning to hold an exhibition of his works once he had completed 50. His death in 1928 meant the target was never reached. The first and only time the paintings were shown together was at the Glasgow Mackintosh Memorial Exhibition in 1933.
It was here that many of the paintings were sold to museums around the world as well as private collectors. Tracking them down has proved the biggest stumbling block to the exhibition.
CURATOR Philip Long began his search knowing that the National Galleries of Scotland owned one of the watercolours and had three on loan from private collectors.
By far the largest collection was held at the Hunterian Museum and Art Gallery in Glasgow, while other works were traced to the Tate museum in London and the National Gallery of Canada.
This has left them with just five paintings to locate, and Mr Long says they are already closing in on them.
He says: "It takes a lot of detective work to track down paintings for an exhibition of this size, and it is not unusual to start two years in advance. We knew where quite few of the paintings were, and it is a case of following clues, old leads, auction house sales and the like.
"It can depend on people not having moved but, so far, the search has gone well. There is some travel involved as it is often best to meet the people you want to borrow from. There is a substantial element of trust, as you are taking something which will have pride of place in someone's collection, so they need to be reassured they will get it back safely.
"There is a private collector in New York who has one of the watercolours and we may have to go out there to speak with him if we want to show the paining."
Hosting the exhibition is a major coup for Edinburgh, as most of Mackintosh's surviving work can be found in or around Glasgow, his home town. Included are works such as Palalda, Pyrnes-Orientales, on loan from a private collection, and Port Vendres, La Ville, which has come from the Glasgow Museums.
Mr Long explains: "Mackintosh was in London in the 1920s and his architecture career wasn't bringing him the same kind of success as it had done in the 1900s, when he designed many of his most famous buildings. After a string of unsuccessful projects, he went with his wife to the South of France for an extended holiday. He wound up staying there until 1927, and during his time he concentrated on watercolours.
"He had always painted in watercolour throughout his career, but this was the first time he had given himself over to it completely, and he created some extraordinary paintings of the French-Spanish border.
"He only painted 44 works, but they are all very intense pieces, highly worked. His plan was to hold an exhibition, but sadly he died before that was possible, and only two of the paintings were ever shown in public in his lifetime.
"When the paintings were shown at a memorial exhibition, many people were shocked because it was such a departure for him. This is a fascinating area of his work that we were keen to look at and explore.
"The paintings coincide with the publication of letters Mackintosh wrote in France to his wife in London, which give us an extraordinary insight into his life and his painting technique."
The collection of letters has been available to the public for research since it was bequeathed to the University of Glasgow by Mackintosh's nephew. They were left with the instructions that they should never be published, but only for research. However, the university became so concerned about mistakes in articles written about the letters that they decided the only way to set the record straight was to publish them.
Roger Billcliffe, vice-president of the Charles Rennie Mackintosh Society in Glasgow and a prolific author on the artist, said: "It will certainly be a treat. It will be wonderful to see all the paintings together under one roof. He is still a very popular artist and I have no doubt that this will attract a lot of people to the gallery."
The exhibition starts on November 26 and runs until February 5 next year
TALENTED TEENAGER WITH A TRADEMARK STYLE
CHARLES RENNIE MACKINTOSH was born in Glasgow on June 7, 1868. He was the fourth of 11 children to William Mcintosh and Margaret Rennie.
Although he suffered from dyslexia, he showed an early talent for drawing. At 16, he decided to pursue architecture as a career.
He met Margaret Macdonald, his future wife, at Glasgow School of Art. In 1927, he wrote to Margaret that she was half, if not three-quarters, of the inspiration for his architectural work.
The Glasgow School of Art is regarded by many as his masterpiece, where he gives full expression to his architectural ideals.
As an artist and an architect, he took inspiration from Scottish traditions and blended them with the flourish of Art Nouveau and the simplicity of Japanese forms.
But, in 1913, he resigned as a partner of architects Honeyman, Keppie & Mackintosh after mounting tensions. The Mackintoshes left Glasgow in 1914 for an extended holiday in Walberswick in Suffolk, and later took a four-year break to the French village of Port Vendres.
He returned to London in 1927, but on December 10, 1928, he died after treatment for cancer of the tongue.