A self-portrait by French Impressionist artist Edouard Manet is expected to sell for between £20m and £30m at a Sotheby's auction in London, potentially achieving a record for the artist as demand for Impressionist art soars.

Next month the 1878 painting, Self-Portrait with a Palette, which has been described as "one of the very greatest self-portraits in the entire canon of art history" by a Manet specialist, will go under the hammer at Sotheby's.