A fresco painting by a Renaissance master which once decorated the bedroom of Pope Alexander VI in the Vatican has gone on show in Rome. A leading Italian art historian and curator says he has documentary proof that it was once part of a much larger painting depicting the aged Pope kneeling in front of his youthful mistress, Giulia Farnese. This is an unusual example of "damnatio memoriae" - a Latin phrase meaning "damnation of memory".