He broke his wand himself in a fit of pique. Nine inches of ebony, unicorn tail hair core; inflexible as the great-uncle he'd inherited it from.
He'd like to remember it differently, but he refuses to indulge foolish desires like wanting to rewrite his own history in a slightly more flattering manner. Lesser people do that, tell stories that change a little with every telling as if they can gradually paint a new picture over the old and forget the original ever existed. Sherlock choses to remember the unedited truth, however unflattering the picture it paints.
That day, he'd been angry and frustrated and, underneath it all, a little ashamed. He hadn't shown the shame, of course, just the anger and the frustration, and he'd taken them out in full on Mycroft on the train heading home, spiteful comments and sharp barbs, and so much nastiness that they've never quite got past it, even now.
Oddly, for all that he's an expert at deciphering the motivations of others, it's taken him until now to pinpoint his own reasoning that day. On the surface it was simple — he was a rebellious child who didn't believe that the rules always applied to him. Rules were there for people who need limitations. Rules were for ordinary people. Sherlock was perfectly capable of setting his own boundaries, so he'd never appreciated having others set tighter ones for him. But, and this is the part that is only just sinking in, it was more than that. He needed magic on his terms, and he'd never had that. He was the youngest in a line of purebloods reaching back to the Magna Carta, and somehow that turned magic into a burden, a duty. Generations of expectations, and that wasn't for Sherlock. He wasn't simply rebelling against the petty restrictions Hogwarts placed on the students; he was reaching out for something different. Something that, with the benefit of hindsight, simply wasn't possible in a wizarding world split in two and terrified by Voldemort.
Maybe his new understanding of his motivation changes things, the way Granger's sudden appearance in the fireplace has changed things.
It wasn't that he needed the reminder. He's always aware of the broken wand on the mantelpiece, what it represents, who he is. That's why he keeps the pieces there. John, though, has never paid any attention to it until now. Never understood the significance of two slim pieces of polished wood with matching breaks.
"I take it that's a wand," John says, once the emerald green flames have died down and Granger is long gone. He's reached his hand out to it three times so far, but hasn't touched it yet. In the last five minutes Sherlock has seen at least a dozen questions flit across his face only to be rejected. It's interesting that John has gone with a statement in the end.
Sherlock doesn't answer: it isn't a question, after all, and the deduction is so obvious John hardly needs confirmation.
"Did they break it, when you were expelled?" John asks, not specifying who exactly he thinks 'they' might be. He's very calm, but then this is John Watson, able to deal with seemingly impossible things with little more than a raised eyebrow and an occasional grimace in Sherlock's direction as though Sherlock's the one responsible. Which of course he often is, directly or indirectly.
"No," Sherlock says. That one word is the most he's ever talked about the day he and Mycroft were taken in front of Dumbledore, two recalcitrant schoolboys. Dumbledore clearly thought his disappointment would be enough to elicit a promise that Sherlock wouldn't break the rules anymore, but Sherlock was used to facing down disappointment. It had no effect on him. And Mycroft evidently felt that where Sherlock was, he should be too, so he'd ensured his own expulsion followed seconds after Sherlock's. And for all that he's never mentioned it since that day, he's never allowed Sherlock to forget it either. Fucking Mycroft, always the elder brother.
"Ah, so you broke it yourself," John says, and thankfully leaves it there. Sherlock doesn't want to remember the feel of his wand splitting, the way the end had sparked, just once, then fizzled out, and something had died inside him at the same time, however much he tried to pretend it was all for the best.
Sherlock feels a familiar urge to shoot something. His fingers are twitching, but when he closes them around an imaginary weapon, they fold into the grip he used to use on his wand. He picks up his violin bow instead, and attacks the first movement of Ysaÿe's Violin Sonata No. 2, and it helps, but it isn't enough. The bow isn't right in his hand; it's a compromise, and Sherlock despises compromises.
The war is over. The world is different, expectations are different. Perhaps it's time. He lifts his hand and sweeps his bow in a figure of eight, muttering old familiar words under his breath. Without his wand it's just a motion and words, but he can still feel the tingle of magic inside him, the certainty he had whenever he cast a spell, when his words could make the darkness go away, when magic lit a fire inside him that nothing else could match.
He flings his bow on the couch, wraps a scarf around his neck — he vaguely registers that it's one of John's, but that's unimportant — and grabs his overcoat.
"Are we—?" John starts, reaching out for his own coat even as he begins to ask some unnecessary question, and Sherlock interrupts.
"Keep up," he says, and takes the stairs at a run. John will be close enough behind him, he's sure of that, and there'll be time for questions and explanations later.
Ollivanders has reopened — Mycroft followed (and no doubt influenced) the progress of the war and made sure Sherlock heard all the highs and lows — so that will be their first port of call. And Sherlock can't wait to show John all the other wonders of wizarding London; if he's fascinated (and pleasingly unfazed) by the application of Floo Powder, he's going to love Flourish & Botts.