Who is Dumnorix from The Conquest of Gaul and what is their importance?

Dumnorix, Diviciacus' brother, is hostile to the Romans. Aware of his stance, Caesar takes him with him to Britain to obviate any trouble he might cause while Caesar is away from Gaul. When he tries to escape from Caesar's army during the embarkation for Britain, Caesar halts the embarkation and arrests him. Dumnorix resists arrest and is killed.