A photograph taken a few days after artist Mondrian’s death in 1944, shows the picture on an easel in his studio in a different orientation. New York City I is one of the Dutch abstract artist’s most important works, but experts now believe it has been hanging the wrong way for decades.

The picture was created in 1941 and was first on display at the Museum of Modern Art in New York in 1945. However, since 1980 the piece as been displayed in the Kunstsammlung Nordrhein-Westfalen art collection in Dusseldorf, Germany.

Curator Susanne Meyer-Buser talked about the history of the artwork at an exhibition for the artist’s anniversary and then stunned the audience by revealing the secret.

She said she’d discovered a photo from Mondrian’s studio, taken a few days after his death in 1944, and the picture (which uses red, yellow, blue and black adhesive strips) could be seen on the easel in a different orientation: with the thicker stripes on the upper edge. Once she pointed this out to the other curators, they realised the picture was the wrong way round.

The artwork will remain the ‘wrong way up’ just in case the strips used in the artwork become loose however.

Mondrian, who was born in the Netherlands in 1872, is regarded as one of the greatest artists of the 20th century.