Christie's says "Head of a Muse," drawn by Raphael as a study for a figure in one of his most famous frescoes at the Vatican, is expected to achieve its estimate of £12m-£16m at the firm's December 8 Old Masters auction in London. If so, it will easily break the auction record for an old master drawing shared by Michaelangelo's "The Risen Christ" and Leonardo da Vinci's "Horse and Rider," which both sold separately for £8.1m.