Caked in dust and dirt, the painting was worth its £100 price tag only for the ornate frame.
Or so the buyer thought when he spotted it in a second-hand shop.
It was only on closer inspection that he noticed an intriguing signature in one corner.
Now the man is enduring an agonising wait to learn whether his find is actually a masterpiece by the French artist Cezanne - and worth £40million.
Art experts say the piece – showing a house with an orange roof next to a river, surrounded by trees – is reminiscent of Cezanne’s earliest works.
Under the scrawled name is the date 1854. If authentic, it will be the earliest known work by the post-impressionist artist who would have been a 15-year-old art pupil at the time.
The buyer, a man in his thirties from Northamptonshire who does not wish to be named, said he had removed the canvas from the frame and removed decades of dirt before examining it.
‘I bought a book on post-impressionism and checked the signature and it looks exactly the same as on some of his other paintings,’ he said.