In his book The Caliphate, Sir William Muir has observed that the history of the period has been colored by the jealousy and animosity between the Umayyads and the Abbasids. When the Abbasids came to power they tried to tarnish the history of the Umayyads. Sir William Muir observes that in these accounts, Marwan the unpopular cousin of Uthman has received constant abuse as the author of Uthman's troubles. Marwan is painted as the evil genius, but all this is tinged by the Abbasid and anti-Umayyad prejudices. Sir William Muir holds that the story of large free gifts to Marwan which formed one of the grounds of impeachment against Uthman reads like a party calumny.