A sting too far? Is this the end for the Fake Sheikh?

On The Press: A court case raises the issue: which comes first, the story or the reporter?

The Fake Sheikh has two problems. He is getting too famous for his own anonymity, and he is failing to convince the authorities of the authenticity of his revelations. Neither of these things concerns me at all; the methods and the morals of his modus operandi do, increasingly.

The Fake Sheikh, for those who have not come across him, is Mazher Mahmood, the News of the World's chief investigative reporter, who likes to dress up as a sheikh to conceal his true identity in the course of his work. This work is to use unconventional methods, sometimes those of the agent provocateur, to reveal criminal activity, or a preparedness to be drawn into criminal activity. It might also be to reveal legal but embarrassing business methods.

The latter would include luring Sven-Goran Eriksson to Dubai to discuss a bogus managerial deal, and coaxing out indiscretions about his players. Or, through seeking public relations advice from the Countess of Wessex, getting her to reveal that she is shamelessly exploiting her royal connections to further her own business.

It is the area of real, or alleged, or contrived criminal activity which is of more concern, and brought the Fake Sheikh back into the news last week. Three men were acquitted of charges that they tried to buy radioactive material for use in the manufacture of a terrorist bomb. The Fake Sheikh, after an anonymous tip-off, posed as a possible seller of "red mercury" to be used in explosive devices. He was working closely with the police in this sting.

The words "red mercury" set alarm bells ringing. In the 1980s, The Sunday Times spent much time and effort investigating claims about this allegedly fearsome chemical. The paper found no evidence of its existence, nor has any other reliable authority since. Yet tales of "red mercury" continue to be hawked around by snake-oil salesmen and "investigative reporters".

The judge in this recent trial was at pains not to criticise the newspaper or the Fake Sheikh or any assertions about "red mercury", but to concentrate on the charges. "It is not about showing distaste for the News of the World's style of journalism," he said. "It is not about cutting Mazher Mahmood down to size."

Defence lawyers were less inclined to play down Mahmood's significance. Stephen Solley QC urged the jury "to send a message to the press that the courts will not be dictated to through campaigns of back-door vigilantism and negative stories".

The crux of the debate, it seems to me, is what comes first - the story or the Fake Sheikh? Journalism should be asking the questions and exposing the corruption of those who want things kept quiet. Journalism should investigate the tip-offs of whistle-blowers. It should not lead targets into temptation.

Journalism is not about entrapment, about setting up the sting and hoping the target walks into the trap. That way, the journalist is a player in the story, not a reporter. Nor, I think, is it about working on joint ventures with the police. It is about working independently and then, if appropriate, presenting the police with the results of that probe.

The public has depressingly little trust in the press. It will suspect the motives of papers setting up stings to get arrests, and stories. And when the public sits on juries, it will be unlikely to convict when the stamp of the untrusted press is on the case.

There has always been a branch of journalism where the story comes first and the facts, hopefully, follow. It is an area where the old cliché "Don't let the facts stand in the way of a good story" is usually just a cynical joke. But when the journalist is a player then the temptation to stand up the set-up grows.

Peter Cole is professor of journalism at the University of Sheffield