The controversial exploits of the 'fake sheikh' who struck fear into the hearts of celebrities

Mazher Mahmood's undercover activities posing as the "fake sheikh" have brought more than 100 criminals to justice, embarrassed the Royal Family, led to a £100,000 contract being taken out on his life and provoked severe criticism of his methods.

The necessarily secretive investigations editor, whose picture byline depicts only a silhouette, is lauded by his bosses at the News of the World with his colleague Conrad Brown. "No wonder politicians and celebrities with dark secrets live in terror of them," the newspaper said yesterday.

Mr Mahmood's reputation has grown with successive "stings". He was made reporter of the year at the British Press Awards in 1999 for his "Toongate" exposé of the Newcastle United Football Club directors Freddy Shepherd and Douglas Hall who, he revealed, had called Geordie women "dogs" and boasted about profits from replica team shirts

The same year, his inquiries led to the London's Burning actor John Alford being jailed for nine months for supplying cocaine and cannabis. Alford had offered the drugs to Mr Mahmood, believing the reporter was an Arabian prince

Also in 1999, the Radio 2 disc jockey Johnnie Walker was suspended after Mr Mahmood and other reporters met him at a London hotel pretending to be interested in setting up a radio station, and filmed him apparently snorting cocaine. Six months earlier, the Blue Peter presenter Richard Bacon was sacked after he admitted taking cocaine during another undercover sting.

Last year Mr Mahmood's investigations embarrassed the Royal Family when the Countess of Wessex spoke to a disguised Mr Mahmood about the services her public relations firm, RJH, could offer. She was accused of exploiting her royal link and later resigned as chairman. The affair led to a review of the business interests of minor royals.

But his activities have also provoked controversy. In September 1999, Mr Mahmood was criticised in court for "ensnaring" the Earl of Hardwicke, who was convicted of supplying cocaine. The earl was given a two-year suspended sentence after the jury made clear he had been the victim of "extreme provocation". Mr Mahmood spent three days in the witness box defending his methods.

Last year a case against Ryan Giggs's brother Rhodri was abandoned after the prosecution said it could not rely on taped conversations between him and Mr Mahmood.

Mr Giggs was acquitted of supplying cocaine, and the judge asked prosecutors to consider bringing charges of incitement to supply drugs, and illegal possession, against the reporter.