Portrait of the Artist, with his Wife and Child seated in a Landscape has been accepted by the Government at a valuation of pounds 1.75m - satisfying inheritance tax liabilities of pounds 1.11m - following the death of the sixth Marquess of Cholmondeley.
The valuation was recommended by the Museums and Galleries Commission, which adminsters the acceptance-in- lieu arrangements on behalf of the Government. Its acceptance followed protracted negotiations. Peter Longman, director of the commission, said that putting a value on a painting of such rarity had been particularly difficult.
It is the only known family group of the artist, his wife and elder daughter, and was painted in Gainsborough's native Suffolk before his departure in 1760 for Bath.
Christie's negotiated on behalf of the marquess, whose grandmother, the Dowager Marchioness of Cholmondeley, had expressed a wish to bequest a painting to the National Gallery.