A painting by JMW Turner is expected to become the most expensive British watercolour sold at a UK auction.
The Blue Rigi: Lake of Lucerne, Sunrise, is predicted to fetch more than £2m when it goes under the hammer at Christie's auction house on 5 June.
The current record for a Turner watercolour on paper is £2.04m, set in 2001 by Heidelberg with a Rainbow.
Christie's said The Blue Rigi is the most important watercolour to appear at auction in more than 50 years.
The painting, described as an extraordinary study in light, colour and texture, was bought in 1842 by its first owner for 80 guineas.
It was one of four watercolours Turner produced on his return from a trip to Switzerland that year.
The 19th Century art critic John Ruskin said of the work: "Turner had never made any drawings like this before and never made any like them again."
The Blue Rigi was last sold in 1942 for 1,500 guineas to the family of the present owner.
Christie's Honorary Chairman Noel Annesley said: "This exceptional watercolour marks the culmination of Turner's achievement in the medium that he made his own, and its appearance at auction offers a special opportunity for both museums and private collectors."
The painting will lead Christie's sale of British Art on Paper.