Howard Marks was a man most wanted. He still is. But not for his drug-running activities. He's the biggest draw in town, as James Rampton discovered, with the launch of his one-man show, in which he reads extracts from his book and talks about his notorious lifestyle.

The press release is headlined: "World's Most Notorious Drug Smuggler to Play Shepherd's Bush Empire." So, it's official: drug-dealing is the new rock 'n' roll. Howard Marks, the man in question, is fully aware of the irony: "I spent years trying to disguise myself and now I'm trying to promote myself," he smiles. "Then I was hoping no one would recognise me, now I'm hoping everyone will."

Marks is hunched over a table next to a book called Hashish. During our hour-long interview, he smoked three joints. They joined the butts of five others already in the ashtray. He has his own customised cigarette papers with "Mr Nice" printed on the packet, and a stash-box sporting a map of Wales, where he hails from.

"There are very, very few occasions when I prefer to be straight," he muses. "The last time was the last day I was in prison. To a lot of people, smoking dope is an aid to creativity." Dishevelled of hair and clothing, he nevertheless retains a sharpness of thought.

During the mid-Eighties, Marks was Britain's most wanted man. He had 43 aliases and ran 25 companies as drug-running front organisations. When he was finally caught, he was sentenced to 25 years. He ended up serving seven years in one of America's hardest prisons.

Since his release in April 1995, he has published his autobiography, Mr Nice (world-wide sales of which have exceeded 100,000 copies), and writes a regular column in Loaded. Now he is being launched on the chat- show circuit as the biggest draw in town.

"I know there are other authors who let the writing speak for itself, but I wasn't prepared to take that risk. I went out and blatantly self- promoted," he confesses.

He sees no contradiction, however, in a criminal who has served his time becoming a star. Marks claims he has paid for his crime of smuggling one- tenth of the world's cannabis. "If I'm out there doing gigs, that means I've been rehabilitated," he contends. "I am now no longer to be considered a criminal, but a writer or a gigger. If convicts aren't allowed to educate themselves and get rewarded afterwards, there's something sick about that.

"People often ask me, `don't you consider yourself still to be making money from crime?' The answer is yes, but I feel fine about that because my crime was breaking a very stupid law. I never had a single ethical qualm about it. It's insane that people like me should be paid millions of pounds for bringing dope in."

He reckons the book has succeeded because it's pressed a button marked "Zeitgeist". The Independent on Sunday has been running a high-profile, circulation-boosting campaign to decriminalise cannabis, and a recent poll in the Daily Mail found 56 per cent of the 18-to-24 age group now favoured legalising the drug.

"The book contains some Boys' Own stuff in exotic locations," Marks reflects, "but essentially it's done well, because most of the readers smoke dope."

Now in his early fifties, Marks does not think he is mellowing as he grows older - in fact, the opposite. "I find I'm losing my rag more with bigotry now. Since getting out of prison, I've made the legalisation of drugs a mission." To prove his good faith, he made a serious application for the Government's post of drugs tsar, and is putting himself forward as Mayor of Palma, Majorca, where he now lives, on a legalisation ticket. He even stood as a candidate in Norwich for the Pro-Cannabis Party at the general election.

"It's payback time, as I did make an awful lot of money out of smokers," he says. "I'd sacrifice my life for the legalisation of all drugs, because prohibition is a huge, huge danger."

What if one of his own four children were harmed by drugs? "I'd question myself quite heavily," he concedes. "I'm pretty sure I wouldn't be changed by a casualty. If one of my children drowns, I'm not going to blame myself for teaching them to swim. Part of the reason I want drugs to be legalised is to prevent them killing my kids.

"Prohibition isn't working," he continues, taking another puff on his spliff. "It's making drugs poisonous and criminal. You might as well ban sailing. Dope-smoking is a voyage of discovery in the head, which is far less dangerous than a voyage on a little boat held together by a white sheet in a storm."

`An Evening with Howard Marks' is at the Shepherd's Bush Empire, London (0181-740 7474) on Friday. `Mr Nice', published by Minerva, is now available in paperback.