The exhibition - a selection from hundreds of paintings completed by the ex-Beatle over the past 17 years - will take place in the small town of Siegen, near Cologne, in Germany. The town was chosen as the venue because its cultural events officer expressed interest in the art - not the artist.
Sir Paul had turned down several previous offers from dealers who had merely seemed interested in his name as the selling point for an exhibition. "He isn't into that. I guess it would be the art equivalent of vanity publishing," said a friend yesterday.
Wolfgang Suttner, cultural events officer of the Siegen-Wittgenstein district, had noted McCartney's passion for painting when he read the 100-page programme for his world tour in 1993.
McCartney's interest in art began at school in Liverpool and developed in the Sixties when, through friend Robert Fraser, an art dealer, he got to know artists such as Andy Warhol and Peter Blake, and started his own art collection. But it was only when he turned 40 in 1982 that he took up painting in studios at his homes in Sussex and Long Island in the US.
"Until then I had this big block in my head that only people who went to art school were allowed to paint," said Sir Paul. "I didn't see it as my place to paint. But when I got to 40, I realised this block was madness. I wanted to paint and the only person not allowing me a canvas was me."
Since then, Sir Paul, who is entirely self-taught, has painted more than 500 pictures in oil and acrylic influenced by Willem de Kooning, a personal friend. They are described as being predominantly in a colourful and emotional Abstract Expressionist style.
His friendship with Andy Warhol is depicted in "Andy in the Garden", painted in 1990. It shows a Warhol-like figure in the autumn evening light of McCartney's home in Sussex.
"Mr Magritte's Ruler" was born out of McCartney's admiration for the artist, from whose estate he acquired a rule and an easel which he still uses.
And "Bowie Spewing", a small work from 1990, is said, by the Kunstforum Lyz gallery in Siegen, to "remind McCartney of a youthful David Bowie".
Another work, a "realistic but ironic" set of three pictures, is a "Salute to the Queen" from the man who accepted a knighthood two years ago.
There are also likely to be some paintings of his wife Linda, who died of cancer in 1998. The exhibition will also feature photographs by Linda which have not been published before.
The Siegen gallery, delighted at its scoop, has described the collection of Sir Paul's works as "fascinating" in the layered use of paint to create his compositions. Sir Paul himself says that often his subject matter is simply an "excuse to put paint on", sometimes directly from the tube or, conversely, so thinly as to be translucent.
He must have been satisfied with at least some of the results. Just two years ago, after admitting to writing poetry, he said he tended to be embarrassed about showing people what he did apart from songs. "The painting I've been doing for 15 years, but I've never exhibited," he told the Independent on Sunday. "And the poetry - I've only just slipped that out of the closet. It's like, bloody hell: all-singing, all-dancing McCartney, what's he going to do next? No, I'm not out to show the world what I can do. I think I've shown the world enough already."
Or, as he put it last week: "I'm not trying to impress anybody except myself."
The Warhol-like figure to the right of 'Andy in the Garden' (above) appeared on the canvas unintentionally as McCartney painted his Sussex garden. 'The paint makes Andy appear, so it is just a magic moment,' says Sir Paul
'Mr Magritte's Ruler', left, was born out of Sir Paul's admiration for the surrealist artist. He uses an easel and a rule which once belonged to Magritte