The portrait is an early work

Ipswich's museum service won a lottery grant to help it buy the painting, Ladies from the Family of William Mason of Colchester.

Ipswich's collection of Constables is now the biggest outside London and the work, which cost �170,000, will hang in the town's Christchurch Mansion

Until last year Constable scholars were unaware of the existence of the painting.

It was found by a fine art valuer during a routine valuation at an unidentified house in East Anglia.

From the outset, Constable was interested in landscapes but was forced to supplement his allowance by painting portraits.

Many of the sitters were known to the Constable family and lived locally.

The Mason family lived in Jupe's Hill, in Dedham, near Colchester, Essex - the neighbouring village to East Bergholt, the artist's birthplace.

Painted in lieu of debt

Ladies from the Family of Mr William Mason of Colchester, still in its original frame, was painted between 1802 and 1806.

It depicts four ladies, whose identities are uncertain, with their dog.

Through the open window is a distant view of a church, thought to represent Stratford St Mary.

Mr Mason was the artist's lawyer, and the portrait is believed to have been painted in lieu of payment of a debt.