"If it ain't broke, don't fix it" summed up the response from the Home Office, and later David Cameron, to the publication of the home affairs select committee's year-long inquiry into drug policy last week. Why waste time on setting up a royal commission into drug policy (something his coalition partners, in contrast, went on to call for) when our current drug policy is working? The key evidence for this, quoted like a mantra by the government, is falling drug use. But the "falling drug use" plank on which the government is walking is a very shaky one.