A long-forgotten sketch by JMW Turner has been discovered in the attic of Kinsham Court, a privately-owned country estate in rural England. The watercolor, which was likely completed in 1796 when the artist was just 21, is heading to auction with an estimate of £30,000-£50,000 ($38,000-$63,000).

The British Romantic artist Jospeh Mallord William Turner is renowned for his highly expressive marine paintings that foregrounded atmospheric conditions and strongly influenced many modernists. The newly recovered sketch will go under the hammer in March at Minster Auctions, a local auction house in England’s West Midlands that is expecting this unusual lot to attract global attention.

The sketch depicts Hampton Court Castle in Herefordshire, not to be confused with Hampton Court Palace in London. In 1796, George Viscount Malden, the 5th Earl of Essex, commissioned Turner to paint the house, which he had just inherited. Turner, who was 21 at the time, had been an exhibiting member of the Royal Academy since he was 15.

Between 1810 and 1910, the house was owned by the Arkwright family. After John Stanhope Arkwright sold Hampton Court he bought Kinsham Court, perhaps bringing Turner’s sketch with him.

The work was discovered by Arkwright’s descendants in a file stuck between various other watercolors that had been left for decades in the attic. These were handed over to Minster’s painting specialist James Pearn who immediately spotted the Turner.

“I have to say, I had a pretty good idea of what it was,” he told the BBC. “This is the excitement of my job, everyday something new comes in.”

The painting was never signed but has been verified. “The signature is in the style,” said Pearn. “He had all sorts of little idiosyncrasies about his technique; the way in which he drew the trees, the way he filled in the shadow, the way he put various combinations of animals together. They’re quite comparable to other examples of his work at this time.”