Attempts to prohibit methamphetamine have caused a cottage industry to scale up. Mexican soldiers last month found 15 tonnes of the banned stimulant, seven tonnes of chemicals used to make it, and a laboratory.

This was the latest sign that meth, once primarily a home-cooked drug, has become a mass-produced one. Unlike cocaine and heroin, meth can be made anywhere. In most countries, the ingredients, principally ephedrine and pseudoephedrine, can be bought as medicine for colds. Cooking them is dangerous. But meth is so addictive that the risk of blowing off your hands stops almost no one.

Asia has seen the same trends. In 2010 Iran destroyed 166 meth labs, up from 33 in 2009 and two in 2008. Much of it was destined for South Korea and Japan: the habit there dates from wartime days. Half of all drug takers seeking treatment in Japan have problems with meth; in South Korea the proportion is more than 90 percent. The UN says Indonesia in 2009 dismantled 35 synthetic-drug labs. In South East Asia, arrests related to meth more than tripled between 2004 and 2009.