An old painting purchased for £100 is due to be sold at auction for £30,000 - as it was in fact painted by the artist Joseph Mallord William Turner.

The owner, who does not want to be identified, bought the watercolour painting of Bishop Vaughan's chapel at St David's Cathedral in Pembrokeshire, Wales as part of a Georgian mansion clearance sale at a Suffolk auction house in the early 1990s. It had been hanging in a dining room for more than 30 years - but after the buyer identified a hidden inscription of 'W Turner' on the back of the painting, experts were able to verify who was behind the artwork.

It's now thought the picture will sell for between £20,000 to £30,000 when it's auctioned with Cheffins auction house in Cambridge on March 20. The owner told The Daily Mail: "The painting was hanging in our dining room for over 30 years - we periodically discussed that the picture could be by Turner but did not take it further. "

The owners added that following a trip to Wales in the autumn of 2022 to visit St David's Cathedral, their interest in the picture was rekindled. They knew about the recent sale of a Turner at Cheffins, so decided to reach out to the auctioneer. Patricia Cross at Cheffins said: "This piece is a significant new discovery which provides a glimpse into Turner's early development as an artist. Born in 1775, Turner was an English romantic painter renowned for his paintings of the country's landscapes and architecture."

St Davids Cathedral in St Davids City Pembrokeshire, Wales, UK (
Image:
Getty Images/iStockphoto)

Turner toured Wales in 1795 at the age of 20, and is well known for having visited St David's, which is when its thought he worked on the painting. At the age of 15, he started showing his paintings at the Royal Academy and his legacy includes more than 550 oil paintings, 2000 watercolours and 30,000 works on paper - many of which he bestowed upon the country. Some of his famous works include images of the Battle of Trafalgar and Venice.

The owner was curious about the painting's origins after noticing the revealing inscription on the back. They identified a painting by Turner online which was not dissimilar in the South Wales Sketchbook, but this was not as developed, and paid a visit to St David's Cathedral.

The painting has been verified by leading Turner scholar Andrew Wilton and is now set to be sold at Cambridge-based auctioneers Cheffins. (
Image:
Cheffins/BNPS)

But it wasn't easy to read because the chapel had undergone repair work since Turner visited. Having taken the painting to the auction house in Cambridge, Turner expert Andrew Wilton was contacted.

Wilton is the former director for the Turner Collection at Tate Britain and confirmed that the painting was, in fact, a true Turner. Its not known where it had been for the previous 200 years before the clearance sale, but some of Turner's paintings - including his depiction of Caenarvon Castle in 1798 - sold for almost £500,000.