Two Jack B Yeats paintings which once belonged to the novelist Graham Greene are due to be auctioned in London next week.
The auctioneers Christie's believe that one of the works by the iconic Irish artist could sell for up to £500,000.
A Horseman Enters a Town at Night was painted by Yeats in 1948 and has never been put on public display.
Jack B Yeats is the brother of the Nobel Laureate poet WB Yeats and won acclaim in his own right as one of the most significant Irish artists of the 20th century.
Many of his works feature images of horses.
In 1948, there was a large exhibition of Yeats' work at the Tate Gallery in London where he finally achieved international recognition.
A smaller painting, entitled Man in a Room Thinking was painted in the previous year. It has a pre-sale estimate of £30,000 to £50,000.
This painting, which measures 8in by 13in, has been displayed once in public - when Greene lent it to an exhibition in London in 1963.
it is understood the paintings are being sold by the descendants of the British author who died at his home in Switzerland in 1991.
The sale on 11 November will also feature works by other Irish artists including Sir William Orpen, Sir John Lavery, Sean Scully and Markey Robinson.