Despite his lack of political experience, and the disapproval of the people of Rome, Claudius proved to be an able administrator and a great builder of public works. His reign saw an expansion of the empire, including the invasion of Britain in AD 43. He took a personal interest in the law, presided at public trials, and issued up to twenty edicts a day; however, he was seen as vulnerable throughout his rule, particularly by the nobility. Claudius was constantly forced to shore up his position—resulting in the deaths of many senators. Claudius also suffered tragic setbacks in his personal life. He married four times (to, in order, Plautia Urgulanilla, Aelia Paetina, Valeria Messalina and, finally, Agrippina the Younger) and is referenced by Suetonius as being easily manipulated. This is particularly evident during his marriage to Agrippina the Younger, his niece. Messalina saw several members of the dynasty eliminated, notably arranging for the executions of Claudius' nieces Julia Livilla, daughter of Germanicus and Agrippina the Elder, and Julia Livia, daughter of Livilla and Drusus the Younger, as well as Julia Livilla's husband Marcus Vinicius, her mother's husband Appius Junius Silanus, Gaius Asinius Pollio, son of Tiberius' first wife Vipsania by her second husband, Claudius' son-in-law Gnaeus Pompeius Magnus, and his parents Marcus Licinius Crassus Frugi and Scribonia. Messalina herself was finally executed after being charged with adultery.