Sherlock and John are students at Hogwarts. Sherlock's trying to get his brother to give him some breathing space, by setting the Ravenclaw up with the captain of the Gryffindor quidditch team (Lestrade). But, his 'wooing' potion needs a guinea-pig. Who better than his best mate, John? Written on a prompt for dunstable on tumblr. Will be a tad more mature as it progresses.