Force of habits: the end for global drug prohibition?

"I've tried probably 150 different psychoactive chemicals," the man with the Israeli accent tells me over the phone. "So I have a very, er, refined palate."

Known to me simply as Dr Z, the man is a mathematician who used to design sleeping pills for a major pharmaceutical company. The drugs he designs these days are more likely to keep you awake. His most famous creation is mephedrone, or "meow meow", which was briefly the world's most famous legal high.

Drugs such as mephedrone usually slip onto the market via shadowy underground networks. Dr Z first tries his creations himself before recruiting willing human guinea pigs from the online "psychonaut" community.

But this clandestine system may soon be a thing of the past. It is understood that Dr Z is now testing a number of drugs in studies conducted by mainstream pharmaceutical labs and costing hundreds of thousands of dollars.

The trials are the result of a radical shake-up in drug policy in New Zealand. Last year its government passed a law that will allow new recreational drugs to be sold openly as long as they meet certain safety standards. Before long, Dr Z hopes, his drugs will be on sale there, alongside alcohol and tobacco - taxed, regulated and entirely legal.

This doesn't mean that New Zealand is legalising drugs: far from it. Existing illegal drugs won't change their status. Nevertheless, the law is a decisive break with prohibition, a policy that has had a stranglehold on international drug enforcement for more than 50 years.

Other countries, too, are breaking ranks on prohibition, leading some to claim that the entire edifice is crumbling. At the very least, New Zealand's radical experiment could provide some answers to the long-running and bitter arguments about whether banning drugs prevents or causes terrible harm.