Newspaper's secret weapon

His high-profile exposés have nailed criminals and caused embarrassment to the aristocracy and the royal family.

As investigations editor at the News of the World (NoW) he has unveiled numerous scandals, and the paper claims he has brought more than 100 criminals to justice.

Earlier this year he was said to have received a death threat in which a £100,000 contract was put on his life.

Mr Mahmood and other NoW reporters infiltrated the gang which allegedly planned the kidnap operation, and became accepted to the point of being given a central role in the alleged plot.

Mr Mahmood was crowned reporter of the year at the 1999 British Press Awards and his newspaper is proud to promote the investigations he carries out.

Many of his stings involve posing as an Arab sheik, earning him the sobriquet "the fake Sheik".

Sophie quits job

It was a guise he used to great effect when he engineered a meeting with Sophie, Countess of Wessex.

The result was hugely embarrassing for the royal family when it was suggested that Sophie was abusing her royal connections as head of her PR firm R-JH - from which she later resigned as chairman.

An investigation into the "social" activities of London's Burning actor John Alford, brought about an eventual police prosecution for supplying drugs.

Posing as an Arabian prince, he met Alford, who fell for his scam, offering him cannabis and cocaine.

Alford was jailed for nine months for supplying cocaine and cannabis in May 1999.

Other Mahmood scalps include DJ Johnnie Walker and former Blue Peter presenter Richard Bacon, who were also captured in drugs stings.

Man of mystery

Mr Mahmood has previously defended his methods.

He said: "I don't think there's anything wrong with journalists exposing drug dealers... I've got 98 criminal convictions as a result of my work, so I must be doing something right."

He is also adept at infiltrating criminal ranks within the Asian community and has exposed numerous immigration scams and bogus marriages.

For a man so skilled at exposing others, Mazher Mahmood is obsessive about maintaining his own privacy.

It is known that he comes from somewhere in the West Midlands, and has worked on the Sunday Times and in television production.

'Entrapment' under fire

The self-styled scourge of the criminal world works secretively, rarely going into the office at News International in Wapping.

Written into Mr Mahmood's contract is a clause stating that his photograph will never be published in the newspaper.

If he features in photos that accompany his stories, his face is always concealed and a silhouette is used next to his byline.

When Mr Mahmood won the Reporter of the Year award, a figure attired in full sheikh's outfit, with the face covered, went up to collect the award - only for the robes to be thrown off to reveal Kelvin Mackenzie, former editor of the Sun.

Although Mr Mahmood has helped to expose crime, many find the way he does it both morally and ethically distasteful.

Lawyers have argued that Mr Mahmood's conduct, backed by the editorial policy of the News of the World, deliberately involves serious breaches of the law.

However, his work continues unabated and he often works closely with officers and says he co-operates with police at all times.