Sherlock scowled at his brother and said, sounding disgusted, "You have a code for this?"

Mycroft nodded once impassively and said, "I have codes for everything regarding you."

"Even if I –" started Sherlock.

"Yes, code five eight two dash C," said Mycroft.

"And I did –" continued Sherlock.

"Yes, code one eight four seven dash Y dash A," interrupted Mycroft.

Sherlock leaned back in his chair and crossed his arms.
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"Why do we have to go first?" asked Sherlock, crossing his arms.

"Because I'm older than you and I said so," said Mycroft drily.

"That doesn't work anymore! We're not children!" said Sherlock, sounding exasperated.

"Then stopping acting like one for God's sake," said Mycroft, sounding exasperated himself.

Sherlock looked at his brother while John and Lestrade stayed quiet, watching the exchange. It didn't do to interfere between the Holmes brothers when they were fighting each other. You rarely left it unscathed as they had learned in the past.
_

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"Do not agree with me, Sherlock. It makes me worry for your mental health," said Mycroft.
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"May I present to you the most abominable human being on this planet. My stalker, Britain's Big Brother, and unfortunately my brother, Mycroft Holmes."