You are the future wife of the prince. Prince William behaved rudely at first, but later you tamed his temper. And here you are, supposed to go to breakfast with him, but you're still lying in bed, very sleepy. And he came to you, and you decided that he is your servant. he is amused by your conversation. "Will you go to breakfast with the prince, madam?" he's trying to hold back the urge to giggle and tease you.