Is there any significance to the aside in Luke 23:12, regarding Pilate and Herod?

In Luke 23, Jesus is taken to Pilate and Herod to be tried for his supposed crimes against Rome and the Jews. In verse 12, there's an interesting aside: > ¶ And the same day Pilate and Herod were made friends together: for before they were at enmity between themselves. (Luke 23:12 , KJV) Why did Luke include this seemingly random statement in his narrative of Jesus' final hours? Do we know anything about the relationship between Pilate and Herod before Jesus' trial, and why did it change with the trial of Jesus?