In the year AD312 Rome is teetering on the brink of war and Constantine's army is on the move. On the Rhine frontier, a Germanic pagan joins the Roman army as a spy, while in Rome itself the pious daughter of a senator finds her self caught in anti-Christian politics. In this edition of Historical Fiction, Tristan Hughes talks to author Bryan Litfin about his novel The Conqueror, which tells the story of the time when the Roman empire was being conquered by the sign of the Cross.