Bruce Anderson: Cameron's drug problem is not with the public, but with the party's traditionalists

Once he was willing to consider legalisation of drugs, but in recent years, he has changed his mind

David Cameron was fortunate. A few years before he arrived at Eton, corporal punishment had been abolished. Otherwise, his drug escapade would have had traditional consequences. As it was, he had to write out a georgic - over 600 lines of Latin verse - and he also forfeited an exeat. He was generally made to feel like a toad under the harrow: quite right too. But the school authorities cannot have taken that dim a view of his character. A couple of years later, he was head of his house.

Eton is a large school, with many articulate and gossipy alumni. So it is surprising that the story did not surface earlier. Inasmuch as it is still relevant 25 years on, three points are worth making. First, David Cameron does not have some concealed druggie hinterland. Two journalists who are writing a biography of him uncovered the Eton story, so he confirmed the details. Otherwise, like Tony Blair, he refuses to answer questions about drugs. I suspect that if they did open up, the two men would have more or less the same to say: nothing much.

Second, Mr Cameron was keen to make one point. As a youngster, he had done some things "which I now regret". He wishes that the media would stress the regrets, for he is determined to say nothing which would in any way glamorise drugs. The last thing that he would wish to do is to make life even harder for parents who are trying to ensure that their children do not transgress.

Like most people who have thought about Britain's drug problem, Mr Cameron is aware of its intractable nature. Drug-takers are responsible for up to half of all crime. Arguably, this is the worst single threat to the British public's quality of life. The drug trade is wrecking Colombia, Guyana, Trinidad and Jamaica, with dreadful consequences for the quality of life and the incidence of premature death. There is talk of a war against drugs. If there is one, we are losing it, and it might be even harder to turn that round than to defeat the Iraqi insurgency.

In view of that, there might seem to be a powerful case for legalisation, and there was a time when Mr Cameron was willing to consider it. In recent years, however, he has changed his mind. A member of his family had a drug problem. Suddenly it was no longer a matter of intellectual arguments, but of personal awareness of the harm which drugs can cause.

There is also a wider issue. A couple of years ago I wrote a piece arguing that there was no realistic alternative to legalisation (for adults). This provoked an eloquent reply from Katie Grant, the Scottish novelist and children's writer. She invited me to put myself in the position of a single mother in Castlemilk, a difficult Glasgow housing estate. Imagine a good woman, trying to keep her kids decent and telling them that drugs are evil. If people like me advocated legalisation, what sort of signal would that send?

Katie was overestimating the Spectator's influence on the debate in Castlemilk. Nor am I persuaded that the mothers of Castlemilk should have a veto on policy changes. Legalising drugs would not be cost-free. At best, it is the lesser of two evils. Yet there are good actuarial grounds for arguing that it would reduce the sum total of misery.

David Cameron is determinedly unpersuaded. He is with Katie Grant and the Mother Courages of Castlemilk. He has given a lot of thought to anti-drug measures, including successful rehabilitation experiments in Sweden and elsewhere. Better treatment for drug addicts would be a high priority for a Cameron Government. But he will not entertain the arguments for legalisation. As he himself has said, he is, too much of a small c-Conservative to do so.

The third point worth considering is the need to keep the whole question in perspective. We are talking about one spliff a quarter of a century ago, not a descent into an opium den in early 20th-century Limehouse. That said, Mr Cameron did develop a dangerous drug habit at Eton: one which he has been trying to kick for many years. He became a nicotine addict. He is now a recovering cigarette-smoker, though it is still far too early to claim a permanent cure. But smoking is a much greater threat to health than the odd spliff.

Let us remain actuarial. A hundred schoolboys go to a party and smoke a joint. A different hundred buy a packet of fags. Whose lives would you rather ensure? A boy who pinches some of his father's whisky is not doomed to alcoholism. A boy who experiments with cannabis is not doomed to heroin addiction. But a boy who starts smoking is hazarding his life expectancy. Nicotine kills far more Old Etonians than cannabis does.

Even so, the coverage of Mr Cameron's schoolboy crime is hardly likely to be actuarial. Eton, drugs, David Cameron, Prince Harry; it is a powerfully narcotic cocktail. Eton's current headmaster, Tony Little, often says that "Eton is a four-letter word". As he observes the way his school is depicted in the media, he may be tempted to use some other four letter words.

It is worth noting that Eton has evolved a sensible policy to deal with drugs. First offenders are punished, though not usually expelled. They and their parents are left in no doubt of the school's disapproval. For the rest of his school career, the malefactor is liable to random blood tests. Failure means expulsion. That is not a bad compromise between the awareness that boys will be boys and the need to prevent breaches of the law. If only it were that easy to deter cigarette smoking.

David Cameron knew that this story was bound to come out at some stage, and is reconciled to temporary embarrassment. It is also unlikely that the voters will be anything like as excited as some newspapers would wish them to be. Most voters know something about teenage boys.

Even so, the whole business will add to one of Mr Cameron's image problems. He set out to change the Tory party. He took it into unfamiliar areas, in order to persuade sceptical voters that the impression which they had formed of the Tory party, and which had led them to vote against it, was misleading. But that, too, was not a cost-free exercise. In the process, some hard-line Tory supporters felt that the party which they had loved and voted for was changing into something unrecognisable.

Mr Cameron had always intended to make 2007 the year in which he tried to reconnect with those Tory doubters by stressing the old themes, including law and order. But the revelation that he himself once had a small problem with law and order will not make this easier. It may persuade some doubting Tories that he is too metropolitan to represent them. Before coming to such a conclusion, however, those Tories should ask themselves how teenage boys are likely to behave.