After arriving in the Wizarding World, Brian had encountered a fair amount of unofficial history. Its authenticity remained open to question, but on the surface, at least, its logic held up.
According to legend, the person who first proposed the concept of wizard dueling once emphasized in a public interview, "A formal wizard duel requires a sufficiently large dueling ground. An informal duel only requires the two sides to meet each other's eyes. If you absolutely must win, ambushing your opponent a day early is also a fine choice. The winner writes history. Everything is for victory!"
After that interview, the Wizard Dueling Committee declared, "This truly violates the spirit of dueling, so we have made a painful yet bold decision." That painful yet bold decision specifically meant issuing a notice stripping the originator of his honorary membership in the association, permanently expelling him from the Wizard Dueling Association, and barring him from all dueling-related competitions.
The story might have been true, or it might have been false. In any case, the dueling ground often ranked among the foremost considerations in wizard dueling. Thus, after considering citizens' practical needs, places where disputes frequently occurred would often establish a secret little room enchanted with an Undetectable Extension Charm. Open the door, and you could fight to your heart's content in the large, spacious arena inside.
Flourish and Blotts often heard exchanges like, "That last copy should be mine!" "Yours? Then who's going to make up for the intellectual nourishment I'll be missing?"
Naturally, it was no exception.
On either side of the dueling platform in the basement of Flourish and Blotts, Gilderoy Lockhart's fans were watching one of the duelists onstage-Gilderoy Lockhart-with rapt attention. Like students in class, they listened carefully as he explained the etiquette required before a duel. That