“We know of no spectacle so ridiculous,” Lord Macaulay famously said, “as the British public in one of its periodical fits of morality.” We seem to be in the middle of a particularly absurd one right now. Although there are many hugely important questions in public life generally, and even a few in the Conservative leadership struggle, what obsesses the media is the attempt to force David Cameron into some sort of confession about drugs. It is ludicrous and shameful.

Cameron has said quite enough about this to satisfy anyone with a proper interest in his past and quite as much as any public figure could be expected to disclose, yet he has been hounded for days. Goaded yet again on Thursday on BBC1’s Question Time, he admitted that like many people he had done things in his youth that he should not have done.

“I’m allowed to have had a private life before politics, in which we make mistakes and do things we should not,” he said. And then he went on to make a perfectly reasonable distinction between his life before politics and his responsibilities now. To any fair-minded person, that should be that. It’s perfectly clear what he means.

To insist that he ought to say more — and I am astonished by the number of liberal and libertarian types who cry out that he must — is in itself rather dishonest. In fact what we’re seeing is not so much a periodic fit of morality as an even more common fit of hypocrisy.

Cameron’s adversaries are hypocritically trying to whip up an anxious moral frisson about drugs to make him look unelectable. I think they are making a mistake. It won’t. Public attitudes to drugs have changed greatly and if the Conservatives are smart they will recognise that.

Almost everybody in this country who is under 40 has been ceaselessly exposed to illegal drugs — at school, at college, in clubs and pubs, at parties and even at work — and there can be hardly any of them who haven’t at least had a tiny puff. People who never have are either unconventional or else older and belong, like David Davis and Ken Clarke if not quite Liam Fox, to the generation in which drugs were still tried only by a tiny avant-garde minority. These days anyone who knows nothing personally of drugs must seem like a total dinosaur to the younger generation; the Conservative party’s problem is not that it’s nasty or stupid, but that it’s extremely middle-aged.

One thing that young people all think is that most middle-aged people, who have no close up and personal experience of drugs, don’t know what they’re talking about. If middle-aged politicians boast publicly of their inexperience of the drug-taking scene as if that were some sign of moral superiority, they make themselves look foolish as well as ignorant. There might well be some interesting blowback in this moralistic attack on Cameron.

Taking recreational drugs is not in itself a moral matter. It has always been one of the greatest pleasures and greatest consolations of humankind, found in all civilisations. Plenty of recreational drugs are legal in Britain, despite their real risks.

It’s true that since some recreational drugs are illegal here it is by definition a crime to take them, and for that reason responsible public figures certainly should not do so. But that does not mean it is necessarily immoral to do so and most younger people don’t think it is. Drug taking is illegal not because it is wicked, but because it can be dangerous.

For many years I did not appreciate how dangerous drugs could be or would become; my generation used to think cannabis was harmless and I have known plenty of people who’ve played around for years with cocaine or with even more alarming drugs without becoming addicts. Fashionable London is said to be thickly sprinkled with the devil’s dandruff. People joke that the lavatories in bars and clubs are crowded with queues of people desperate for a line and we hear lurid tales about celebrity coke heads, but given the millions of times that people take drugs, it is surprising how few addicts there are.

It always seemed to me that the few who drifted towards addiction were driven there by other problems — some by their own addictive personalities, others by the poverty of their lives or their expectations. It is one of life’s many injustices that the people most likely to get into serious trouble with drugs are those who are already in some other serious trouble, and the law does not seem to protect them.

That is why for years I used to be firmly in favour of decriminalising drugs; I thought that despite the increased risk involved — possibly, to some — it put an end to drug pushing, to habit-supporting crime, to contaminated drugs and to the vast evil empire of the illegal narcotics trade.

All the same, as my children have been growing up I have gradually realised that drugs seem to be getting nastier and evidence of the long-term damage they can do has been mounting. Even contemporary cannabis, grown hydroponically, is several times stronger than the gentle weed of the 1960s and 1970s, and skunk can quickly trigger psychotic episodes in a small minority of susceptible people. It even has a name — skunk psychosis. I’ve seen it in someone close to me. It is terrifying and it has made me suddenly much less sure about decriminalisation. With the democratisation of drugs, the privileged trips of the 1960s have turned into a dead-end highway.

The question of what to do becomes more pressing. The law as it stands does not seem to protect the vulnerable, rather the reverse. Yet nobody seems to know and perhaps there is no way of guesstimating whether decriminalising drugs would make things better or worse. Understandably nobody is willing to make the experiment. All one can say is that ignorance and moralising merely obscure the problem.

Last Friday it emerged that a close relation of Cameron’s has been receiving treatment for heroin addiction; some commentators may claim that this, too, will somehow count against him in the leadership contest. On the contrary, compared with the professed ignorance of his three rivals, his more youthful knowledge and experience so far from being a mark against him should be a mark in his favour. Hypocrisy doesn’t always prevail.

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