<P> Arthur (Clive Owen) is portrayed as a Roman cavalry officer, also known as Artorius Castus, the son of a Roman father and a Celtic mother, who commands a unit of Sarmatian auxiliary cavalry in Britain at the close of the Roman occupation in 467 A.D. Arthur is loyal to Rome and a devout Catholic, but follows the teachings of Pelagianism, which many consider heretical . He and his men guard Hadrian's Wall against the Woads, a group of native Britons who are rebels against Roman rule, led by the mysterious Merlin (Stephen Dillane). </P> <P> Arthur and his remaining knights Lancelot (Ioan Gruffudd), Bors (Ray Winstone), Tristan (Mads Mikkelsen), Gawain (Joel Edgerton), Galahad (Hugh Dancy) and Dagonet (Ray Stevenson) expect to be discharged from their service to the Empire after faithfully fulfilling a fifteen - year commitment . </P> <P> However, on the night when they are to receive their freedom, Bishop Germanus (Ivano Marescotti) sends them on a final and possibly suicidal mission to rescue an important Roman family living north of Hadrian's Wall . Marius Honorius (Ken Stott) faces impending capture by the invading Saxons, who are invading from mainland Europe, led by their king Cerdic (Stellan Skarsgård) and his son Cynric (Til Schweiger). According to Germanus, Marius' son Alecto is the Pope's favourite godson and may be "destined to be Pope one day". Though angry, the knights follow Arthur once more but only after he and Lancelot argue over Arthur's deeply held beliefs . </P> <P> At the remote estate, Arthur discovers that Marius has immured pagans, including a Woad named Guinevere (Keira Knightley) and a small boy named Lucan . Arthur defies Marius and frees the captives before deciding to take everyone, along with Marius' family, back to Hadrian's Wall . </P>

Who played the leader of the saxons in king arthur