The presence of Lord Balrus inside Miranda was purely political if not just for spying. The rumors of the ambush went from being discreetly, to now being publically known except for the fact Lord Leoric was playing part in it. The Lord of the Mines denied of having any part in the war and he even said the Prince came to his city not to seek men, but rather to ask if his men can pass through while they march North. This he said he accepted it, but he wasn't offering Prince Ambrose anything.
Aprophil and Lord Balrus spent a significant amount of time together ever since the ships left Whitebridge harbor, while Prince Amabel spent his time with his generals talking about the plans and going them over all the time.