One hopes this latest victim won't resort to the tactics of one of Mahmood's previous targets. In 1997, the News of the World ran a story claiming that Paul Moyle had offered a hit man pounds 5,000 to have Mahmood gunned down. The hit man turned out to be another reporter. "He's worse than the police," the paper reported Moyle as saying. "Other villains won't do business with me since I've been in the paper."
Even after being sacked by The Sunday Times for deception, Mahmood received the industry stamp of approval: he was voted Reporter of the Year in March for scoops including his exposure of the Newcastle chairman and vice-chairman Freddie Shepherd and Douglas Hall last year. His editor has good cause to be pleased. While other Sunday tabloids have slumped, the NoW's sales figures remain healthy at 4.313 million.
Little is known about the man himself. The paper uses a silhouette of his face for a picture byline. Mahmood, known as Maz to friends, is in his mid-thirties, from the West Midlands, and is the son of a magistrate. NoW editor Phil Hall rates Mahmood as "the best reporter in the business by a long way. He's extremely bright, intelligent and very, very careful. I can't remember a libel writ against him, and we have millions of letters each week."
Others are less enthusiastic. Publicist Max Clifford is critical of the way Mahmood operates. "He came up to do an interview with a client, and as soon as my back was turned, he was trying to persuade the client to deal with him directly. It was nipped in the bud, but that's the kind of thing he does. I have been dealing with the editor of the News of the World for years, and Mahmood's the only reporter who's ever done that. It speaks volumes."
Mahmood is, apparently, equally careful in his elaborate subterfuges, using a camera lens the size of a drawing pin, which he conceals in his jacket lapel. "You have to be able to think on your feet," said Hall, citing a recent example in which Mahmood posed as an Arab. "He didn't realise the contact was going to bring an Arab with him. He started to speak in Arabic and Mazher turned it on his head by going into a complete rage, shouting at the subject and saying, `This is an insult to my nationality and a terrible insult to my host country'. It can be very dangerous. He has a minder with him all the time. He must be the only reporter in the world who regularly has people turning up on his doorstep at 6am."
While Mahmood's track record is beyond doubt, his methods are not. There have been allegations of "cannibalism", a reference to the fact that he has repeatedly exposed immigrant scams, such as the staged weddings which help illegal entrants to Britain to get visas.
"There's an unease in the fact that as a non-white journalist, he spends an awful lot of time exposing black and Asian crimes," said one journalist, who declined to be named.
Phil Hall denies this: "I don't think he does any more Asian stories than others. He's of Asian appearance and so he's going to mix in those circles." He added: "We have done a fair few immigration scams. But he would never do a set-up. If somebody comes to us and says `Johnnie Walker is doing drugs and I will supply them and you can catch him', we'd run away from it. It has to be the person you are targeting as the perpetrator and instigator of what's happened."
Media commentator Roy Greenslade wrote what Hall called a "hatchet job" on Mahmood, following the Newcastle expose. At the time, Hall was quick to respond to the criticisms: "I am amazed you have printed such an extraordinary, unbalanced attack... one sometimes has to use subterfuge to nail the bad guys. If it's in the public interest, what's the problem?"
Public interest is precisely the problem, said Greenslade. "You have to treat every story on its own merits. You have to ask: is there a public good being served on this occasion? There's a fine line between setting someone up, and catching them in the act. I know the problems the NoW has had in catching someone in the act. They have to prepare a scenario, because it's the one way they can get tape or video recording. And at that, Mazher is the world's greatest living expert.
"The rule of thumb, based on my instinct, is this: is the person being exposed acting in their private life, or did their public position warrant that they were guilty of gross hypocrisy? With the Newcastle story, I decided there wasn't enough public good. These two were lured into a very neat set-up, and I don't think it was right."