What can a German do but a Briton cannot? What can a New Yorker, a Chicagoan and a San Franciscan do, but a Londoner cannot? What can Canadians, Dutch, Portuguese, Chileans, Uruguayans, Maltese all do? The answer is they can legally smoke cannabis. In California there are now courses for cannabis sommeliers. In Britain they would be thrown in jail.

Half a century ago, Britons prided themselves on being in the vanguard of social progress. In such matters as health care, sexuality, abortion, crime and punishment, they considered their country ahead of the times. Now it limps nervously in the rear.

I don’t use illegal drugs, neither am I addicted to nicotine or alcohol or fatty foods. Having sat on two drugs-related committees, I accept that narcotic substances can, in varying degrees, cause harm to their users and, through them, to others. If after half a century of a “war” on drugs, banning had solved or even reduced this harm, I could see the argument for banning. It has not.

Roughly a third of adults in England and Wales aged under 60 have tried cannabis. Almost 8% use it occasionally and 2% regularly. Far fewer use hard drugs. But nearly one in five residents of English and Welsh prisons are estimated to have been jailed for a drug-related offence. Half of all homicides are drugs-related. In many prisons, more than half the inmates use drugs regularly. The authorities turn a blind eye for the sake of peace and quiet.

Successive home secretaries have a terror of even discussing the issue. Tony Blair delegated drugs – as so much of his policy – to the Daily Mail and the Sun. While other countries researched, experimented and piloted innovation, Britain simply shut down debate. When, in 2009, the government’s chief drugs adviser, Prof David Nutt, evaluated the relative harm of different narcotics, he was sacked.