A life-size portrait of Sir Winston Churchill, which he said revealed his soul during one of his darkest hours, is going on public display after years spent hanging on the wall of the home of his late grandson.
The 1916 portrait was painted before Churchill became prime minister, but after he resigned from his post as First Lord of the Admiralty over the failure of the Gallipoli campaign in the First World War.
It is the work of Sir William Orpen, one of Britain's best-known portrait painters and war artists.
On seeing the painting, Churchill is said to have told the artist: "It is not the picture of a man. It is the picture of a man's soul."
The artist himself spoke of the misery expressed in Churchill's face.
The painting is going on display tomorrow at the National Portrait Gallery in London, in a long-term, 10-year loan.
The loan follows an agreement with the estate of Churchill's grandson, the late Winston Spencer Churchill, who died in 2010 and had the painting for many years in his house.
The portrait was painted in the year of the Dardanelles Commission, in which Churchill was preparing to defend himself against charges of incompetent and reckless leadership.
The commission went on to conclude that he was not personally responsible for the failure of the operation.
The National Portrait Gallery said that Churchill regarded the painting as the finest one of himself.
It said: "Orpen's portrait captures an important moment - a crisis in Churchill's career - which evokes a very different impression from that of the defiant hero of later popular imagination.
"This questioning, deeply personal portrait illustrates a painful episode in Churchill's early career, offering insights not only into the sitter, but also of the harrowing responsibilities of military leadership during the First World War."
National Portrait Gallery Director Sandy Nairne said: "I am very pleased that the Churchill family has agreed that this outstanding portrait by William Orpen of Winston Churchill, the nation's greatest 20th century statesman, should now be on public display."
The painting was briefly on show at an exhibition at the Imperial War Museum in 2005, but it is otherwise thought to have remained in the former prime minister's grandson's home.