Bella blinks at the mention of Mr Mayer's name - the most interesting thing about him up until now has been the link between has accent and Sherlock's. He's an adequate teacher, not the worst she's had and certainly not the best, friendly enough with his students, and never seems to be around to answer questions between classes.

She is just going to have to find a way to ask him questions anyway. There's no reason for Sherlock to be her only resource if she has access to another.

"Yes," she says, "that doesn't seem as though it would have been very effective for any of you."

(It pretended to be my dad, was all Cal Chandler had been willing to say about his experience, more interested in fiddling with a lighter than meeting her eyes, and she had had to be content with that.)

"It could at least be partially filtered out. Headphones with the music turned up."