"Tower of the Koutoubia Mosque was created following the Casablanca Conference where it was agreed by the Allied forces that only complete surrender by the Axis powers would be acceptable," Nick Orchard, head of modern British art at Christie's in London, said in a statement.
"It is the only work that Churchill painted during the war, perhaps encouraged by the recent progress made by the Allies in what he considered to be one of the most beautiful countries he had encountered."
Orchard added that the artwork is "arguably the best painting by Winston Churchill due to the significance of the subject matter to him, and the fact that it highlights the importance of the friendship between the two leaders."
"The gifting of the work to Roosevelt underlines the fact that Churchill held the American President in such high regard and points to their joint efforts in guiding the Allied powers to the outcome of the Second World War," he said.
According to the New York Post, Churchill's artwork was last sold for approximately AUD $3.7 million in 2011 by New Orleans antique dealer M.S. Rau. And it was reported that the buyer was Pitt, who then gifted the priceless painting to Jolie while they were married.
Jolie and Pitt married in 2014, after meeting on set of their 2005 film Mr. and Mrs. Smith, but announced their separation in 2016. However, the pair are yet to finalise their divorce as they battle over custody over their six children: Maddox, Pax, Zahara, Shiloh, Knox and Vivienne.