Decriminalise the personal use of all class A drugs.
Why does this idea matter?
Drug users should be helped and not criminalised. This would reduce the costs of policing, the courts and the prisons. It would also reduce criminal activity as a lot of crime is undertaken to feed drug habits. It may also have an indirect effect on the outcome of the Afghanistan war as the price of heroin would plumet and cut off valuable resources to the Taliban.
Some of the cash savings could be invested in rehabilitation centres and getting addicts back into work.