IF YOU type the words “Tony Blair, Daily Mail, humiliating” into Google, it will provide you with 9,620 results. The nature of internet search engines is such that not all of these will be stories about the Prime Minister in that newspaper in which he was indicted with that term — but if only 5 per cent of them were, then it would represent a striking pattern.

If you repeat the same exercise for “Charles Clarke”, then a slightly more modest range of about 600 references can be culled from cyberspace. The latest of these occurred on Saturday when the Daily Mail, echoing the words of David Davis, the Shadow Home Secretary, accused the Home Secretary of a “humiliating” flip-flop by asking for policy on cannabis to be reconsidered.

Being a flip-flopper is a badge that Mr Clarke should wear with honour. As a broad rule of thumb, any official statement that the Daily Mail condemns or lampoons is probably in the public interest. It strikes me that the Home Secretary has been eminently reasonable in pressing the Advisory Committee on the Misuse of Drugs to look at fresh reports on the impact of cannabis on the brain and to examine whether different strains of cannabis should have different classifications. I would also argue that none of this means that David Blunkett was wrong to heed previous counsel and in January 2004 downgrade cannabis from a Class B drug to a Class C one. Information, like cannabis itself, is supposed to be mind-altering.

There are those, such as Simon Jenkins, Mary Ann Sieghart and Matthew Parris, who have taken an interest in drugs policy for decades. I cannot claim such devotion. I rarely think of it at all and am often uncertain when I am obliged to give it attention. In this, I suspect, I am, for once, in tune with the vast majority of the population.

For confusion appears to be the most rational position to hold on this matter. As a matter of general principle, I dislike the thought of banning things. Prohibition rarely works effectively and I’m thus inclined to permit people to weigh up the costs and benefits of a course of action for themselves and make their own mistakes if that is what follows. Intellectually, when it comes to cannabis — and other drugs — I am a liberaliser bordering on an outright libertarian.

Yet theory and practice are often distant relatives. To think of a decision to start or continue using drugs in such cool and rational terms is utterly unreal. It is not the same as judging the relative merits of a night spent in watching television or going to the theatre. Taking drugs is a process that often begins under peer pressure, or lubricated by alcohol, or during a period of emotional trauma. Once started, the nature of physical or psychological addiction swiftly overcomes the capacity to engage in lucid calculation as to whether it is wise to keep taking drugs.

How one engages in a cost-benefit analysis of taking cannabis when one side, armed with sober medical data, insists that it is the equivalent of heroin-lite, while another camp, with its own clinical surveys, asserts that it does no more harm than herbal tea, is beyond me.

In the real world the claims that “all drugs are bad and must be banned” and “all freedom is good and must be exercised” have pretty limited value. In these circumstances the best approach for politicians is to appreciate that an open mind is not an empty mind (and is better than a small one), that the evidence is likely to be fluid and inconsistent, and that the truth lies somewhere in the murky middle.

To which, some will retort, Mr Clarke’s intervention smacks more of politics than an elevated interest in medical science. This might be right, but I would put forward three reasons for a less cynical interpretation. The first is Mr Clarke’s attitude to this subject when he was a junior minister at the Home Office from 1999 to 2001. Back then he had his doubts about the advantages of cannabis reclassification or decriminalisation.

The second is that when the main threat to the Labour Party at the polls is that of middle-class defections to the Liberal Democrats, implying that you might reverse one of the policies of which metropolitan leftie luvvies thoroughly approve is hardly an obviously cynical tactic.

The third is that indicating that the Government might, in retrospect, have made a mistake is to invite the likes of the Daily Mail to crow about “humiliation”.

It is deeply unfortunate that this last factor matters so much, so often. We are in danger of creating a Catch-22 in which if politicians refuse to switch position in the light of new facts they are accused of being “arrogant”, yet if they do, then they are berated for being “feeble”, “inconsistent” or “weak”. The pragmatic U-turn is a much underappreciated manoeuvre in the Highway Code of political conduct. It is far preferable to driving straight ahead and over a cliff.

The actual debate we should be having about cannabis, and other drugs, is what is the purpose of the classification system. It is, currently, threefold. First, to indicate to the public the comparative dangers associated with various illegal substances. Secondly, to provide a rationale for the varied severity of sentences to those who sell or “push” these substances. Thirdly, in my view more dubiously, to indicate a similar scale of punishments for those caught possessing these items for personal use. At the risk of being slated as “feeble”, “inconsistent” or “weak”, I have never understood why it helps any individual who is addicted to drugs, or society at large, for there to be a risk of imprisonment for that desperate situation.

John Maynard Keynes observed that: “When the facts change, I change my mind, what do you do?” This is not, alas, an approach that the Editor of the Daily Mail endorses.

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