As regular readers will know, we often note the passing of the regular British ritual where the UK government asks a group of scientific advisers to give evidence on the harmfulness of drugs and then ignores them.

The unwritten rule is that everyone feigns mild exasperation and then goes about their business as if nothing had happened, but the Home Secretary Alan Johnson has gone and spoiled the party by firing neuroscientist David Nutt, the head of the drugs advisory committee, for, well, waving that damned evidence about.

The home secretary’s officially sacked the chief adviser for breaking what turns out to be a non-existent rule about discussing government policy in a recent lecture – using the carefully mischosen words “I cannot have public confusion between scientific advice and policy”.

Subsequently, two other scientists from the advisory committee have resigned and both the government’s Chief Scientific Advisor and the Science Minister expressed their dismay.

An evidence free drugs policy isn’t a British speciality, unfortunately, as shown by a recent World Health Organisation study that showed that severity of drug laws around the world have virtually no relation to the drug use of the population.

So why did the home secretary break the unwritten rule about quietly ignoring the evidence in the service of some pointless sabre rattling? Surely nothing to do with the fact that a general election is coming up.