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Pet Squirrel on the Block: Christie’s in London will auction an extremely rare painting on April 15, Hans Holbein’s 1528 masterpiece “Portrait of a Pet Squirrel and a Starling.” It is being called the most important work to come on the London market since Vincent van Gogh’s “Sunflowers” and is expected to set a record for an Old Master painting in a London sale. Proceeds will help preserve the historic Houghton Hall in Norfolk, built for Robert Walpole, England’s first prime minister.