There's a petition on the 10 Downing Street website which actually makes sense:
Heroin addicts are known to steal and commit crime to pay for their habits. If the cost of heroin to the addict was reduced to zero by prescribing it on the nhs (subject to counselling) the reduction in expenditure in police time spent due to related offences could be used to offset the cost. It may even be cheaper for the government to do this, and it may also be possible for these heroin addicts to then find suitable employment, through the use of a counselling system, which would enable them to earn money and pay tax. (which could further be used to pay towards the cost of the treatment)
Go on, sign it.