Some wars are unwinnable. Take Prohibition in the 1920s and early 30s, when America made the consumption of alcohol for recreational purposes a criminal offence. We all know the result: gangsterism (think Al Capone), rampant money laundering, the rule of law brought into contempt, corruption, alcohol-related violence, an epidemic of alcohol poisoning through illegally produced ‘liquor’ and a corresponding upsurge in mental health problems and addiction. In short, Prohibition achieved precisely the opposite of what it set out to achieve.

How then, eighty five years after Prohibition was repealed, are we still making the same mistake? I refer, of course, to the ‘war on drugs’.

First, let’s nip in the bud any suggestion that our current policy of criminalising drugs is winning that ‘war’. According to the National Statistics Office, in 2016/17, around 1 in 12 adults aged 16 to 59 in England and Wales had taken an illicit drug in the last year. And although this represented a fall from the 2006/07 survey, drug experts are warning that more potent and harmful narcotics are flooding the illegal market.

When it comes to drug use among children in England, in 2016, 24 per cent of pupils reported they had taken drugs, including a shocking 37 per cent of 15-year-olds. Ironically, many teenagers say it is easier to get hold of cannabis or cocaine than legal drugs like alcohol or tobacco.

One of the most worrying trends concerns cannabis use. To set this in context, the last Labour Government under Gordon Brown made a decision to reclassify cannabis from Class C to Class B, ignoring swathes of advice from police, doctors and experts. As in 1920s America, this prohibition merely allowed the drug cartels to operate beyond all control.

Ground-breaking research by GW Pharmaceuticals, which makes medicines derived from cannabis, and King’s College London found 94 per cent of samples seized by police were varieties with a high psychoactive content, suggesting they dominate the illicit market. The researchers warned of “concerning implications for public health”. This means that almost all cannabis seized by police now comprises high-strength varieties, with outdoor-grown herbal strains and hashish barely found.

This matters because it suggests a growing number of people are at risk from mental and psychotic illness from smoking super-strength cannabis (‘Skunk’) or, even more alarmingly, taking artificial cannabis (‘Spice’). Indeed, the problem is almost out of control in our prisons.

Ironically, the original home of Prohibition, America, is increasingly tolerant of marijuana. Half of US states have legalised cannabis to some degree and in California recreational marijuana will be openly sold from next month in licensed premises. Just as alcohol taxes reap a fortune for the UK government, so for legalised narcotics in America. In Colorado an annual $200m in drug taxes have flowed into schools and clinics rather than the offshore money-laundering accounts of drug barons.

In countries as diverse as Portugal, Denmark, Switzerland, Germany and the Netherlands – to name a few – hard and soft drugs are being brought under the regulation of the state rather than gangsters. And it is revealing that there exists no market in the Netherlands for synthetic cannabis, precisely because the real thing, like alcohol here, is legal.

So what, you might say. UK law is the law of the land and drugs like cannabis are illegal. Those who do the crime must do the time. Politicians almost en masse are terrified of appearing ‘soft’ on drugs. Never mind the chronic harm to individuals and society caused by excessive alcohol consumption which should, at the very least, question the reasoning behind keeping drugs illegal.

I would argue it is high time for a mature, pragmatic, rational debate on this issue. Above all we must accept the ‘war on drugs’ is not winnable. Personally, I suspect there is something deeply human about indulging in narcotics like alcohol or other psychoactive substances: few societies in history have not used drugs. Perhaps too much reality can be unbearable. If so, the point of the law must surely be to help people avoid unhealthy excess and tightly regulate harmful substances.