A recent study in New Zealand found that 25 per cent of young males commit a criminal offence in their teens or early twenties. Ninety per cent of them never get to court - they are let off with a police warning or an apology and most never appear in the crime statistics again.

The major problem is how to best deal with the much smaller group of young offenders who do come to court, especially the 5 per cent who may commit up to 50 per cent of all youth offending. They are unexploded time bombs.

How we deal with this group is one of our country's biggest challenges. These persistent offenders, who too often start their criminal careers before they become teenagers, are doomed to graduate to adult jails unless something is urgently done.

Maybe this fast growing problem is becoming apparent elsewhere - or maybe not.