Drugs are no longer the great stigma they once were at Westminster. The most dramatic indication of this came seven years ago when Ann Widdecombe stood up at the Conservative Party conference to propose that people caught with even the smallest amount of cannabis should be fined £100. Seven of her front-bench colleagues promptly admitted that they had smoked cannabis at university, strangling Ms Widdecombe's silly "zero tolerance" policy at birth. On the Labour side we have had similar admissions of youthful indiscretion from Charles Clarke, Vernon Coaker, Caroline Flint and the late Mo Mowlam. In all, 32 current MPs have owned up to having taken drugs at one point.
More damaging when it comes to drugs these days are accusations of lying, or hypocrisy. So what are we to make of the revelation that the Tory leader, David Cameron, was disciplined for smoking cannabis when he was at school? In the 2005 Conservative leadership election, Mr Cameron refused to answer questions about whether he had ever taken drugs, although admitting to "typical student experiences". Throughout the media frenzy that attended that election, he never said anything that now disgraces him.
It is instructive to compare his behaviour to that of Charles Kennedy. The former Liberal Democrat leader insisted that he did not have a drinking problem right up to the point it emerged he had received treatment for alcoholism. By contrast there has been no "cover-up" over Mr Cameron's past. That is why, despite the fuss that will inevitably be generated by this revelation, the Conservative leader's reputation will survive unscathed.
So much for the politics. But what about the principle? The truth is that it is of minor importance what politicians did before they entered politics. It is far more important what they propose to do once they are there. And it is somewhat ironic that Mr Cameron is far more sensible on the subject of drugs than either his Tory predecessors or the present Government. He has demanded intensive rehabilitation for drug addicts rather than prison, showing an understanding that addiction cannot be cured by imprisonment. And last month he said he would be "relaxed" about legalising cannabis for medicinal use.
Indeed, reforming drugs policy has been one of the themes running through Mr Cameron's career since he entered Parliament in 2001. He sat on the Home Affairs Select Committee, which produced a bold report in 2002 on the subject of drugs. He supported the Government's downgrading of cannabis from class B to C in 2004 and suggested that the Government should consider doing the same for ecstasy, too.
It is true that there is a growing body of opinion that says some of the varieties of cannabis available today, in particular "skunk", are more dangerous than they were in the past. But this does not alter the fact that heavy-handed prohibition is failing. Mr Cameron's emphasis on reducing harm is the only sensible way to proceed.
It is interesting that the shift in attitudes towards politicians and past drug use over here seems to be echoed on the other side of the Atlantic. In his political memoir, the new Democratic presidential candidate, Barack Obama, admitted to taking drugs while a young man. Things have moved since the days when Bill Clinton felt, under heavy questioning, that he had to deny inhaling.
If any good is to come out of such revelations it will be a less hysterical debate about drugs policy. There are strong signs that the public is far less one dimensional in its attitudes than parts of the media and the political establishment believe. Almost a third of adults in this country have taken some form of illegal drug. There is a growing awareness that present policies are not working. At least now we seem to have a generation of politicians who know a little of what they are talking about.