and court time. The most common of Mahmood's stings is to persuade his celebrity victim to procure cocaine for him. (Incidentally, in the opinion of an experienced criminal QC, in actively requesting the purchase of cocaine Mahmood and his immediate bosses - who provide the money - are committing the offence of conspiracy to possess a controlled drug.)

In one of Mahmood's highest-profile cocaine stings, the radio DJ Johnnie Walker was eventually convicted of possessing 0.06 grams of cocaine - about a fiver's worth - and was fined £2,000. The paper, however, has never been charged with any offence committed in compiling these reports.

However, after a series of failed stings on the Duchess of York, on Prince William's friend Guy Pelly, on the MP George Galloway, and even on the Blairs' friend Carol Caplin, the fizz seems to have gone from his stories.

At the same time, since the entrapment and subsequent filming of Max Mosley at his S&M parties landed the paper in court for invasion of privacy - with at least £500,000 to

pay – the paper's reliance on prurient, celebrity sex romps looks to have been neutered. Where will they go from here?

Over the last 20 years or so, celebrity stories have become an internationally traded commodity, prompting Rupert Murdoch in 1994 to appoint Piers Morgan, a gossip columnist, to the editor's chair at the News of the World. Traditional stories of rapacious vicars and mendacious MPs made way for reports of any vague misdemeanour that could be attached to a well-known face.

The strategy appeared to work - the News of the World is currently the biggest-selling newspaper in Britain. But the paper has come to rely largely on reporting techniques that consistently verge on the illegal or libellous.

Now that they are being regularly challenged and found at fault, unless editor Colin Myler orders a retraining programme for his staff in legal, old-fashioned and painstaking methods of investigation, it's hard to see how they'll keep the readers coming back.