Knives are simply a fashion accesory for kids these days and it's a status symbol to carry one unfortunately.
Just last week a very good mate of mine was chased round a car park of a pub by a nutter with a knife and the reason was that he wanted to extort money on a weekly basis from his hairdresser shop.
Stick these cowardly cunts in a boxing ring and see how far they get
Think is that you can't stop it at all as every household in the UK has knives in the kitchen so getting hold of a chopper really is simple as you like.