A painting British artist John Constable kept by his side until his death in 1837 is to be auctioned at Sotheby’s in December.
The Lock, which depicts work on the River Stour in Suffolk, is estimated to be worth £8m-12m.
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.”
It was last sold in 1855, since when it has remained in the same family collection for more than 150 years.