Every time I watch The Blind Banker, this little thing "bugs" me. Just after the scene where Sherlock retrieves the jade hairpin from Amanda (Olivia Poulet), and she freaks out about it ("Nine million!"), there is a shot of London before the next scene begins. Over the music you can hear a buzzing sound, like bees or wasps. Why!? I'll probably never get an answer to this, but just thought I'd put it out there