The painting was given as a token of friendship and respect between two giants of 20th century world affairs. Painted by Sir Winston Churchill in Morocco in 1951, it was presented two years later to the American general George C Marshall, author of the Marshall Plan.
The Marshall family treasured it for years, blissfully unaware that it was unknown to art experts and Churchill scholars, despite references to it in Churchill's papers lodged at Cambridge University.
But when Kitty Winn, the general's granddaughter, and a star of films including The Exorcist, came forward to sell it, she was staggered by the £250,000 value placed on her grandfather's memento by Sotheby's, London, which will sell the painting on Monday. Typical prices for Churchill were around £120,000 until last year, when one of his paintings sold for £344,000.
Sarah Thomas, a British art expert, said: "Churchill's market has shot through the roof recently. I'm sure it's to do with the general interest in 20th- century British art because a lot of collectors have realised that it's an undervalued area. And there's a special interest in Churchill. The painting is significant because it has missed the radar."
Churchill produced the scene in Marrakesh during a visit to Morocco to compose his memoirs. The country was the site of the Casablanca Conference in 1943 - the first meeting with President Franklin Roosevelt on mutually foreign soil. General Marshall was the US Chief of Staff.
Churchill painted a landscape for Roosevelt, while another was given to General Dwight D Eisenhower. By the end of the war, he decided he would like to pay tribute to Marshall, a man he descibed as "the noblest Roman of them all". The occasion came in 1953 when the general, who had just won the Nobel Peace Prize for his programme of economic relief for Europe, was invited to Queen Elizabeth's coronation. Later the same week, Churchill presented him with View of Tinherir - a town on the desert side of the Atlas mountains. Kitty Winn remembers seeing the painting at her grandparents' home in Virginia when she was growing up.
"I first saw the painting when I was a child. I don't think I knew the significance of it, but I knew it was given a place of honour in my grandparents' drawing room," she said, adding that it was a difficult decision to sell.
"I loved the painting, it's an extraordinary work and as I've got older and know much more about Churchill and their relationship, it's given it a richer history than I understood as a child.
"It's been in my family for over 50 years and I think it's time it was out in the world and seen by lots of other people.
"It's an amazing testament to these men's relationship to each other and that particular [period of] history."
Ms Winn said she was surprised to discover that its existence was not known to the rest of the world as there were letters referring to it in the Churchill archive at Cambridge University. "There's a letter from the Marshalls to the Churchills talking about the painting and a letter from my mother thanking him. I just assumed that other people knew about it," she said.
Marshall's wife, Katherine, wrote to Churchill to tell him they considered it "a gala day" when they hung the painting. "It has added so much to the beauty of our drawing-room and has the place of honour," she wrote.Reuse content