Constable painted The Lock between 1824 and 1825 - and the work, which depicts a scene on the River Stour in the artist’s native Suffolk, has now emerged for the first time in 160 years.
The painting, which was the fifth in a series of six landscapes known as ‘Constable’s Six-Footers’, was made in response to the huge critical acclaim that greeted his first treatment of the composition. Constable loved the painting so much he held onto it until passing away in 1837 at the age of 60.
Following Constable’s death, the picture was offered alongside other major masterpieces in a sale of works from the artist’s studio. It was sold to Charles Birch, a leading collector of the day, for £131 and ten shillings.
Birch later fell on hard times and, in 1855, auctioned off the painting when it sold for £860, a record for any Constable that remained unchallenged until the Hay Wain was sold in 1866.
The painting was bought by William Orme Foster, part of a family of Worcestershire industrialists, and it remains in this family.
Now one of just three major Constables remaining in private hands, The Lock is to be sold by Sotheby's next week at its auction of Old Master & British Paintings in London.
Experts have given the painting an estimate of £8 to £12 million. However, with art prices on the up, there is a good chance The Lock could sell for significantly more.
Julian Gascoigne, Sotheby's senior British pictures specialist, said: "Constable's absolute mastery as a landscape painter is everywhere in this picture - in the vigour of the almost impressionistic brushwork, in the drama of the clouds and the changing weather, even in the movement of the grass in the fields and the sparkle of water as it cascades through the lock.
"It is one of those pictures that captivates, and the more one looks, the more one sees."
The painting will be exhibited in Hong Kong, New York and Los Angeles, before leading the Old Master & British Paintings Sale on 9 December.