Have your talk with Arche Duke in the room

You smile at both of them before saying, "Well, I think congratulations are in order."

The Arche Duke bows his head to you and says, "Thank you, my new King, now if it is within your will, can we please take our leave? We have much planning to do."

You chuckle underneath your beath as this is the part you have been waiting for. "I am utmostly sorry, but I can not allow you to leave yet. Not at least until Lady Beatrice returns the parts of the Queen's wardrobe that are currently in her possession."

The Arche Duke "With all due respect My new King, But who is Lady Beatrice, and how does that individual have my future wife wardrobe."

You throne at the man "Do you not know your future wife's first name? In case you didn't know, it's Lady Beatrice. And as for her wardrobe, she owns no clothing. She gave up those clothes when she gave up her title to marry you."

The Arche Duke looks over at your mother, who is looking back at him in shooks. "SHE DID WHAT?!?"

You answer him, "Of course, she would have to give up her title to marry you. This kingdom has just lost its King and eldest Prince. I am more than happy to approve your marriage under the condition we set forth. However, you can not expect us to make the royal line any more chaotic than it already is. That shouldn't be a problem for you since you are only marrying her because you truly love her"

The Arche Duke nervously rubs the back of his neck. "Yes, yes, of course, No problem at all. Just us go shopping to buy her clothing first."