I'd been trying to use Belstaff as a b-word for weeks and nothing was working out. floppybelly suggested the origins of Sherlock's coat, and my urge to write more irritated, protective Mycroft just took over.
John picks the great coat up off the floor, where Sherlock's dumped it, and hangs it up. Dusting it off slightly, he turns to Sherlock.
"You should really take better care of this thing. Where did you get it, anyway?"
Sherlock freezes, the memory rushing to the forefront of his mind.
"Sherlock, please take the coat." Mycroft draped it over his shoulders, rolling his eyes when Sherlock simply shrugged it back off.
"Fuck off, Mycroft."
"If you're going to live in this hovel and waste your money on drugs and cigarettes, the least you can do is let me give you one article of clothing. Look at you, you're shivering."
"I don't need your bloody charity. And don't try to tell me it was yours first, your waist hasn't ever been this narrow."
Mycroft grimaced – if Sherlock was making petty barbs about his weight again, there was no use in arguing. Gently, he took the coat and folded it over the back of the single chair in Sherlock's filthy flat, silently letting himself out.
Later that night, waking clammy and feverish – from hunger, or withdrawal, he wasn't sure – Sherlock grabbed the coat and pulled it up over his skinny frame.
John's voice snaps him back to the present day. "I mean, honestly, it couldn't have been cheap. It's a bloody Belstaff."