Sir Leon casually mentioning that he threw some noble in the dungeon in his report.
Arthur: Wait what did he do??
Leon: Oh right. He gifted Merlin sweets and asked if he wanted to have a picnic with him, Sire. But his family is an important ally, so I had to refrain from executing him.
Arthur, now very confused and trying hard not to let his jealousy show because he wants to be a good, just king: Leon courting Merlin is not a crime
Leon confused as well: Well of course it's not written down like that. But courting the kings... Uhm *clearing his throat and staring at the floor awkwardly* lover is quite disrespectful.
Arthur now blushing furiously sputters: Merlin?! My lover?!
Leon: Uh Sorry I didn't mean to offend you... Or him! I just thought you wanted the marriage to stay secret. I mean yes he always is carrying Queen Ygraines sigil with him but I just-
Arthur: LEON! Merlin is my servant. I'd never- I can't- He's just my servant nothing more. Please tell me you haven't told anyone of this crazy assumption of yours
Leon, disbelieving after a loooong moment of silence: My CRAZY assumption!?!? Wha- YOU'VE BEEN UNDRESSING HIM WITH YOUR EYES EVERY TIME YOU TWO ARE IN THE SAME ROOM!!! I didn't have to tell anyone!!!
Arthur: So who else thinks-
Leon: EVERYONE!!!!!!!!!!!!!!!