It was the communist revolution that expunged opium. Mao Zedong , with his political apparatus that reached into every hamlet and home, was able to lay the beast low as he repressed so many attributes of human nature, both good and bad.

It was a mixture of carrot and stick. Addicts were not condemned but offered medical help and rehabilitation. But those who were unco-operative were sent to labour camps or imprisoned. Dealers were summarily executed, often without trial.

China was clean for 40 years, until the demise of Mao. Gradually opium has returned. Now the mainland is one of the world's most important opium growers. Although it still regularly executes drug traffickers, demand in its freewheeling economic society finds willing suppliers prepared to take the risk. As a Chinese proverb puts it: 'If you open the window sunlight comes in, but so do mosquitoes.'

Government attitudes on the mainland have not changed. But the black market is a match for government, as it is almost everywhere.

The black market grows by the decade and repression, unless it is totally totalitarian, leaves enough loopholes for the determined to wriggle through. The zeal to repress in most countries of the world has become counterproductive, building up the wealth and criminal reach of the drug barons who have become so powerful that they often have a political influence that distorts, even threatens, good governance.

By all accounts their influence is growing and the various types of control - from Europe's tolerance of soft drugs but toughness on hard, to Beijing's rigorous policy on executing dealers - are clearly not working. At least in Hong Kong there is a reasonably informed and intelligent debate. On the mainland, as in many parts of America and Europe, debate is barely tolerated.

Of course, heroin addiction is in another league than opium. Towards the end of the 19th century, heroin, a derivative of opium, was discovered by a German chemist working at the Bayer company - the same laboratories that gave us aspirin. It is heroin that can cut an addict to pieces faster than any other drug. Although, let it be said that many people who have taken heroin moderately have lived quite productive and acceptable lives; witness the poet Coleridge.

Hard drugs may be forbidden today in Britain and Hong Kong - dare we ask how Sherlock Holmes would have had the insight to catch his criminals in today's London without his white powder? But, at least, unlike in most though not all states of the US, there is no longer any debate about its medicinal uses. This is why, if you are dying from some painful cancer, it is probably best to die in a hospice in Britain as my mother did - one of the few countries to allow the use of heroin as a pain suppressive, the strongest painkiller of them all.

The truth is that neither China with its millennia of centralised government nor the US with its technological prowess is a match for the drug traders. The tough policies of the mainland, Malaysia, Singapore and Thailand, which execute minor traffickers, have rarely touched the big barons.

We either do what Mao did - allow our governments to be simply totalitarian on this issue and implement a scorched-earth policy - or we legalise opium and other drugs to break the back of the underworld trade. We then deal with addiction by educational and medical means. It is the present and almost universal 'in-between' that is so unsatisfactory and so dangerous.

Just days ago, the former president of drug-ridden Mexico, Vicente Fox, surprised the country by saying it was necessary to legalise drugs in Mexico, arguing that this would pull the rug from under the murderous drug barons who can only make their huge profits when drugs are prohibited.

This is how it should be - in China, the United States, Latin America, Nigeria and Europe. No other policy will defeat the drug mafias.

Jonathan Power is a London-based journalist