The right idea, but probably unworkable, and leaves the police to decide whether the carrier is OK or not (ie knife for fishing, or fighting - difficult call, and a lawyers dream?). Brown's idea of 'over 16' prosecution just means gang members get under 16's to carry the knife for them, till needed!
Quite a number of years ago, I was involved with a knife and weapon amnesty. When it came to sorting out the bins, in the main it was the responsible person who had handed something in. The villains or wrongdoers still retained their prized possessions.Okay you got the odd Samurai ornamental sword or the Davey Crockett designed masterpiece, but these were from the collector more than from a participant of lethal crime.
Don't forget, in this modern day, its cool to carry and use a knife, if respect is challenged.
I presumed the thinking was deterrent, should only take a few 'high profile' jailings start to make the yobs think twice about carrying knives - so prisons would not have a continuous overcrowded situation. But, then again, capital punishment never stopped murders - so perhaps there isn't an answer to the knife problem.
ps Is the problem only an 'English' one - as it seems from 'day2strike' that only English jails are full!!