Duncan had to withdraw.
Because it wouldn't be long before the news of his slaying of God's Whip - Attila would spread across Europe, and Aetius would know by the latest tomorrow.
But at this point, Aetius probably couldn't do anything about it.
Exile Camp.
Duncan was now writing a letter, in the capacity of Governor of the Province of Britannia, to the Emperor Valentinian III. This was not a letter of loyalty, but a detailed account of the Battle of Sharon, from his leading the British Legion across the sea to the end of the Battle of Sharon, including matters regarding Aetius and his suspected act of letting Attila escape, leaving a gap in the encirclement for the enemy to break through.
The last part detailed Duncan's strenuous effort to kill the empire's great enemy, God's Whip, in vivid detail, immersing the reader in the scene. It's likely that even Valentinian III would be thrilled, as this young, weak emperor, long manipulated, was eager to prove himself just once.