An oil sketch by John Constable missing for 40 years has been discovered in a private collection in Guernsey.
The sketch shows Willy Lott's House at Flatford, which appears in The Hay Wain, the most famous work by the 19th Century English landscape painter.
Its location was last recorded in 1979, when it appeared in a rare Italian scholarly publication listing Constable's work.
The oil on canvas, dated June 1814, is 11.5in by 9.6in (29.2cm by 24.4cm).
The house featured was a symbol of the rural way of life that was so precious to Constable.
Tenant farmer Willy Lott lived in the house for more than 80 years - reportedly only spending four nights away from the house in his whole life.
It is in the tiny hamlet of Flatford, on the north bank of the River Stour in Suffolk, which is at the centre of the area now known as "Constable Country".
John Constable (1776-1837)
Born in Suffolk, the son of a corn and coal merchant, he worked for his father before studying at the Royal Academy Schools from 1799, with his first exhibition at the Royal Academy in 1802.
Constable believed that his paintings should come as directly as possible from nature.
He made hundreds of outdoor oil sketches, capturing the changing skies and effects of light - using these sketches as the basis for larger exhibition pieces which he scaled up in his studio.
Constable painted locations in his native county, as well as Salisbury, Brighton and Hampstead; and travelled to Norfolk and the Lake District.
In 1829, he was elected to full membership of the Royal Academy.
Although his work is extremely popular today, Constable received little other recognition in Britain during his lifetime, but he had some success across the English Channel and had a profound influence on French Romantic artists.
Auctioneers Martel Maides said research by experts had confirmed its provenance by tracing the sketch back to the artist's grandson.
Jonathan Voak, paintings specialist at the auction house, said: "The re-emergence of this oil sketch will make an important contribution towards establishing the chronology of Constable's oeuvre.
"Dated June 1814, it provides an important point of reference against which other undated works can be compared.
"This beautiful, freely-painted, oil study is a rare combination of a work by a great artist that has both historical significance and aesthetic appeal."
The sketch is due to go to auction on 21 September with a guide price of £80,000-120,000.