A nude portrait by Francis Bacon, of the Soho model Henrietta Moraes, has sold for £21m at Christie\'s in London. The painting had been in the hands of a private collector and has not been seen in public for 15 years. The amount was one of the highest fetched by a work of post-war contemporary art at Christie\'s. The current record for a Bacon was set at Sotheby\'s in New York in May 2008, when one of the Irish-born artist\'s Triptychs sold for $86.3m (£55m). Bacon painted more than a dozen portraits of Moraes, a familar Soho denizen who also posed for Lucien Freud. Francis Outred, of Christie\'s, said the painting sold this week was \"one of the most seductive and sexually-charged\" he had ever encountered. The £21.3m price - paid by an anonymous bidder - was more than £1m above the auction house\'s top estimate. The same event also saw a Lucien Freud etching sold for £145,250 - the highest amount that one of the late artist\'s prints has ever fetched at auction.