Haddo House is one of Britain's most northerly stately homes. Tucked away in the wilds of Aberdeenshire, it has been home to prime ministers and earls - but is it also home to some of Scotland's greatest lost paintings? Nearby, in the storerooms of the Montrose Museum lies a mystery painting with a giant hole in it. The portrait shows Richard Mead, the patron of one of Scotland's most celebrated painters, Allan Ramsay. According to the history books, the painting is a copy of a painting in the National Portrait Gallery in London. But has there been an unfortunate mix-up, and is the painting in London in fact the pretender?