It looks like a harmless teenage prank - training shoes dangling from telephone wires in a quiet suburban street.But for residents in this affluent neighbourhood it is a sign of something far more sinister. It tells them violent gangs are operating in their midst.This picture was taken last week in Kensal Rise, North West London, close to the homes of celebrities such as Jade Jagger, Zadie Smith, Louis Theroux and Vogue Editor Alexandra Shulman.This method of marking territory was first adopted by gangs in the Los Angeles ghettos but can now be seen across Britain.A local youth in Kensal Rise, who called himself Gaz and claimed to be a member of a street gang, said the trainers indicated that there were dealers of the drugs in the area, and were put there as a 'respect thing'.