Henry: We just have to keep it very casual, of course.
Alex: Oh. Obviously. The press and all.
Henry: I just can’t afford for you to fall in love with me.
Alex: Oh.
Henry: Okay, wait a minute. No, that’s not what I meant when I…
Alex: Get over yourself, Your Majesty.
Henry: It’s “Your Royal Highness.” I don’t know how many times I have to tell you that.
This quote comes from the movie ‘Red, White & Royal Blue’. The movie is based on a novel of the same name written by Casey McQuiston. | Red, White & Royal Blue is produced by Amazon Studios
Movie vs. book
In the novel Alex is not that kind of a person that would be confused about which title to use with Henry. He does use a lot of funny alterations of his title when writing emails to him, for example: “His Royal Highness Prince Henry of Whatever“.