It's never been easier, or cheaper, to buy drugs online – but no one knows what's in them, or how dangerous they are. For most of the last decade, an average of four or five new legal drugs came on to the market each year. Then mephedrone appeared on the scene: cheap, legal and available online. By 2010, the drug had become the fourth most popular drug, after marijuana, cocaine and ecstasy. It was banned in April of that year, but not before a new market had emerged for online legal highs. In 2011, EU researchers found 49 new legal drugs for sale online. In 2012, 73 were identified; hundreds more were banned.