This is how I think the conversation should have gone in Buckingham Palace after Mycroft informs Sherlock of The Woman's profession.
Don't own anything!
How it should have gone!
"Don't be alarmed. It's to do with sex." Mycroft said patronizingly.
"Sex doesn't alarm me." Sherlock replied defensively.
"How would you know?" Mycroft said with a smug smirk.
"Oh, I know!" Sherlock said nonchalantly.
"What? How do you know?"
"Psh, you know…"
"How come I don't know!"
"You can't know everything about me, Mycroft!"
"Yes I can! I know all there is to know!"
"No, not this one!"
"You don't know."
"You can't know."
"So you don't know."
"I didn't say that!"
"So, you know?"
"Ha, you'll never know."
Mycroft turned to John.
"Did you know?"
"No." John said after sipping his tea.
"So he doesn't know."
"How should I know?"
"You're his flat-mate!"
"Exactly, why should I know?"
"He knows all about you."
"He's Sherlock, he just knows!"
"By any chance, are you two…?"
"No! No, I'm not gay! How many times do I have to say this?"
"I know you'd know if he knew, John."
"NO! Jesus Mycroft, he's your brother, why are you discussing this with me?"
"You're, well, you know…"
"No, I don't know. I wouldn't know and I wouldn't want to know!"
The palace official looked confused "I lost track of the conversation, what's going on?"
John looked at him sympathetically, "You don't want to know!"
Ya… I don't know where this came from or what went on in that last bit either, don't ask! I was thinking about how Sherlock could have gotten back at Mycroft and how the word play would go...