 A year later he was Proconsul of Cisalpine Gaul.In 115 BC Diadematus was elected Censor and during his censorship with Gnaeus Domitius Ahenobarbus they expelled 32 Senators from the Senate.He was an opponent of Lucius Appuleius Saturninus and when Saturninus in 100 BC tried to oppose the Senate by means of force, together with other Senators they went to arrest him.