It’s something any avid watcher of Antiques Roadshow dreams of – to find a set of rolled up canvases in the attic, the forgotten horde of an artist. It happens, and sometimes it happens to the artist themselves, as it did last year to abstract painter John McLean who had forgotten that he had stored a number of canvases in the cupboard of an American friend some 30 years ago. Rediscovered by chance when the friend was cleaning out her cupboards, the haul is the subject of a forthcoming exhibition at the Fine Art Society this month.

“John had taught in a lot of art schools,” says Emily Walsh, Director of the Fine Art Society in Edinburgh, speaking of the Courtauld-trained artist who became one of Britain’s leading abstract painter in the late 20th century. “He was invited to lecture at the Boston Museum of Fine Arts in 1982, but discovered when he got there that the post had been reduced to one day a week. He lived a hand to mouth existence,” says Walsh. McLean filled in the time by painting, but when the job finished he didn’t have enough money to ship the works back to the UK. “A friend said, give them to me and I’ll keep them until you can ship them over, upon which they both forgot all about it.”

The works are typical mid-career McLean. “I think the critical change in his work came on that trip when he went to Emma Lake in Saskatchewan, a place he kept returning to,” says Walsh. “His work got brighter and bolder and he engaged with a lot of American abstract painters who were like-minded – there was no one doing the same thing in the UK, really, aside from Caro.” The vibrant pictures in this coming exhibition, lost in a cupboard for so long, are a unique snapshot from a vital moment in the artist’s career.

John McLean: The Boston Pictures, The Fine Art Society, 6 Dundas Street, Edinburgh, 0131 557 4050, Until 10 Nov, Mon – Fri, 10am – 6pm, Sat 11am – 2pm