They're wearing black Doctor Marten boots, long black coats and black T-shirts with the names of their favourite nands on them. Some of them are wearing lipstick and eyeliner and a few of them have piercings. Nervous shoppers hurry past them, trying not to make eye contact. It seems to be quiet but you feel that at any moment a fight could start. The police say these young people are probably harmless-perhaps they just hang around the square because there's nothing better to do.