Lord Julian is very young for the position he finds himself in, as Regent of the Levant. It does establish the role he steps into in the next book as Darien's Chancellor/Steward over the Vexin. Someone's got to manage all the money the Vanguard is taking home... and let's face it, between him and Libbet, the Vanguard's finances are in loyal and effective hands.
Darien is many things, but having ANY idea what to do with money is not, exactly his forte.
Val would buy swords, and more swords.... and a few more swords.
Lloyd would grumble, horde it all like a dragon, and stab anyone that came close.
Ashot... would rob everyone blind.
Stephen would wail, and try to give it all to the poor.
Wylan would be too focused on Darien to even notice the money.
This is where I began to realize how VITAL Libbet was to the Vanguard. They simply aren't prepared for what comes next, and her and Julian are.