I believe (probably wrong) that he's dressed as a Hussar, who had a bit of a reputation for being the Mr. Steal Your Girls of the Napoleonic Era. Mustaches were fashionable in Britain and France in the Victorian Era because of them; the original and best Hussars were from Eastern Europe, nations like Poland and Hungary, where men tended to grow mustaches if they could, and so when Western European armies added them to their cavalry forces they wanted to adopt their looks, and the image of the dashing and moustachioed cavalry officer bled into civilian life.