source for the following info: i have lived 4 years in London, between 2007 and 2010.
London is bad. There are vast areas of London that can only be described as "ghettos", where the population is almost exclusively black and/or otherwise migrants, again almost exclusively from poorer countries. Kids are absolutely awful, just about every kid i spoke with told me "when i grow up i want to be a gangster" or variations of the same. None can speak proper english, they have an absurd view of life, some even want to join al-quaeda because "fight the power". I'm not making this up. The level of ignorance among kids in most London suburbs is shocking, be it Peckham, Croydon, Stratford, Hampsted Heath, it doesn't matter. They are so lost and without guidance that they have "postcode wars", where if you are from one postcode, you automatically hate everyone from the other postcode.
Stabbings are a daily occurrence. Kids of any age will go around carrying knives, because it's what you do in London.