John Constable sketch initially deemed a copy sells for almost £100,000

The sketch of Dedham Vale with Brantham Mill, on the Essex/Suffolk border, was previously dismissed as a copy

A Constable oil sketch previously believed to be a copy has been auctioned for £91,000.

The painting of Dedham Vale was sold by Sworders' auctioneers on Wednesday.

John Constable, best known for 1821 masterpiece The Hay Wain, used the sketch as the basis for his "Dedham Vale, Morning" picture.

Sworders' Sarah Flynn said the inclusion of one of his father's mills in the picture "makes it a particularly personal image".

The sale price of £91,000 is inclusive of buyer's premium, an additional charge made by the auctioneer on top of the amount an item is sold for at auction.

Sworders' said the sketch was rediscovered by its London office having previously been dismissed as a copy by another auction house.

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Pictures specialist Ms Flynn took it to Anne Lyles, a world-renowned authority on Constable.

She declared it "an exciting new discovery".

Constable (1776-1837), was believed to have painted the 26.5 x 43.5cm (10½ x 17¼in) sketch in 1809-10.

Sworders' sold the Constable oil sketch for £91,000

The picture, called "Dedham Vale with Brantham Mill and haystacks", had previously hung in a private house in London for many years.

It features the distinctive tall tower of Dedham Church and, across the River Stour, a windmill at the village of Brantham.

The windmill is believed to have been owned by his father Golding Constable, who the BBC's Who Do You Think You Are programme discovered was distantly related to East Enders/Carry On actor Barbara Windsor.

John Constable's 1821 painting The Hay Wain depicts a scene at Flatford in the Dedham Vale and it hangs in the National Gallery in London

John Constable also painted this view of his father's kitchen garden in East Bergholt, Suffolk

The most famous representation of the panorama is Constable's "Dedham Vale, Morning", which he exhibited at the Royal Academy in 1811.

The sketch had been sold to Major AW Allen, an ancestor of the latest sellers, in 1946.

Ms Flynn said: "It is the dream of every auctioneer to discover a picture by one of the greats of western art.

"Dedham Vale is intimately associated with Constable's life, but the inclusion of one of his father's mills in this picture makes it a particularly personal image."

This portrait of John Constable by Ramsey Richard Reinagle hangs in the National Portrait Gallery

John Constable

• Born in 1776 in East Bergholt, Suffolk, John Constable is best known for landscape paintings of the English countryside

• The title of his masterpiece, The Hay Wain, refers to the wooden wagon (wain) used for transporting cut and dried meadow grass (hay)

• The wain was pictured at Flatford in Suffolk, which lies between Dedham and Manningtree

• Constable was never financially successful and he sold more of his works in France than in his native England.

• Constable died in London on 31 March 1837