If we compare the official language that Richard used to describe not Edward V, but Edward IV, with Henry’s official descriptions of Richard, the former seem far more vituperative, after Richard had changed tack and decide to excoriate his brother. If anyone indulged in propaganda with a view to actively blackening a predecessor’s reputation, it was Richard, not Henry. Compare Henry’s bland proclamation shortly after Bosworth (fresh enough that it contained the erroneous information that the Earls of Surrey and Lincoln, as well as Viscount Lovell, had all been killed there) with Richard’s damning references to Edward. Henry refers to ‘Richard duke of Gloucester, late called King Richard’, but gives us no further description, either of the king or his rule. Richard, by contrast, happily went into details about Edward IV in Parliament, with references to Edward’s ‘ungraciouse pretensed mariage’ and the result that ‘all poletique rule was perverted’.
— David Horspool, Richard III: A Ruler and His Reputation