It lay forgotten for decades among a pile of dusty exercise books, pens and staplers in the back of an old school cupboard.
But this painting – discovered by pupils of Roedean School in Brighton when clearing out an old headmistress’s office – could be worth up to £1 million.
The painting was in a dusty package wrapped in plastic which they almost threw in the bin.
But when they unwrapped it they found a forgotten work by British painter John Constable.
Titled The Chain Pier Brighton In A Gale, it is understood to have been painted when the artist, most famous for his masterpiece The Hay Wain, visited the seaside resort in the 1820s.
On the rear is a bill of sale which states that the painting was bought from the artist’s grandson Hugh Constable and exhibited at the Constable Exhibition in 1900.
It was then auctioned in 1909 by Christie’s as a J. Constable R.A. and sold for £31 10s.
It was sold by Christie’s at the same time they sold a much larger painting of the pier by Constable which is now in The V&A.
Richard Chamberlain, Roedean’s senior deputy head, said: ‘A couple of the girls and I were waiting to attend a school event one evening and we were chatting outside the room that was, many moons ago, the headmistress’s office.
‘One of the girls asked what was now kept in there and I said I believed it was just used as a stationery cupboard, so we had a look.
‘To our absolute amazement, when we unwrapped the small package at the back of the room we found the painting. After some research in the school archives we found it was donated in 1955 by former pupil Beatrice Weber and the school magazine reported it as a Constable at the time.’
Three pupils at the £35,000-a-year girls school – Mary McHarg, 18, Amirah Mehdi, 17, and Eris Kennish, 17 – accompanied Mr Chamberlain to Christie’s in London to check the authenticity of the painting.
Eris said: ‘It’s like something out of a storybook that the painting was found hidden away like this. It’s just amazing.’
Mary said: ‘I’m an art history nerd so it’s exciting that a piece of art like this was just sitting here in the school I go to. I couldn’t believe it.’
In 2012, Constable’s The Lock – painted at about the same time as the find – became one of the most expensive British paintings ever sold, fetching £22.4 million at auction at Christie’s in London. It is thought Chain Pier Brighton In A Gale could be worth up to £1 million.
Although it has yet to be officially authenticated, the school wants to come to an arrangement with Brighton Museum to display the painting. A spokesman for Christie’s said they could not comment on values or estimates for works of art that are not consigned for sale.