ONE deeply-felt conviction unites the thousands of demonstrators who will be marching through the streets of London today: that the law banning cannabis is an absolute ass.
It may not be a view shared by the Government, but it cannot simply be brushed aside. The protest will show that the campaign to legalise the drug now reaches far beyond the ranks of the young and rebellious.
The marchers will be led by the Labour MP Paul Flynn, supported by a number of prominent European MPs. A liberal broadsheet is giving the campaign its backing. And it's not just the fashionable bien-pensants who think the present law is unworkable. The Mail's Ann Leslie has argued powerfully in this newspaper that cannabis should be decriminalised.
Their case can seem beguiling. The law in this matter is more honoured in the breach than the observance. Academic studies suggest that half of all 16-year-olds have experimented with the drug. Millions of adults have puffed the occasional joint without coming to any noticeable harm. And it is arguable that cannabis is less injurious to health than either alcohol or tobacco.
Yet when all that is said, today's demo still does not deserve to succeed.
Yes, the ban on cannabis may indeed be ineffective. But then, so are the bans on harder drugs such as heroin and cocaine.
There were just 333 registered addicts in 1958. Today the number hooked runs into tens of thousands. Despite police successes - like yesterday's arrest of a Turkish drugs baron - junkies can all too easily find a fix.
But should the law be changed simply because it isn't always obeyed?
Only the most extreme libertarians take the view that hard drugs should …