Journalist who claims to have put 100-plus criminals behind bars
Dubbed the "Fake Sheikh", Mazher Mahmood has spent 25 years as an undercover reporter with everyone from celebrities to royals caught up in his famous exposes.
But his credibility was placed in doubt after the judge in the trial of Tulisa Contostavlos accused him of telling "a knowing lie" in a pre-trial legal hearing.
Known to his colleagues simply as Maz, he claims to have helped put more than 100 criminals behind bars and risked his life on a daily basis to lift the lid on the murky world of crime.
Paedophiles, arms dealers and drug dealers have all found themselves at the centre of Mr Mahmood's stories. So too have celebrities and public figures, including the Countess of Wessex who was taped calling the Queen "the old dear", and Sven-Goran Eriksson who revealed his plans to quit as England manager.
During his evidence in the trial of the former X Factor judge, Mr Mahmood told Southwark Crown Court he spoke to his driver, Alan Smith, after he had given a statement to police.
Mr Smith told police he heard Tulisa speaking out against drugs. The court heard the driver later changed his statement after speaking to Mr Mahmood.
But during the pre-trial hearing, Mr Mahmood denied that he and Mr Smith had discussed what was said in the car.
Judge Alistair McCreath, who had ruled that bad character evidence against Mr Mahmood could not be heard before the jury, said this "constitutes the clearest evidence that Mazher Mahmood told me a knowing lie".
Mr Mahmood's journalistic practices also came under the spotlight during the trial.
He told the court he began probing Contostavlos after receiving a tip-off that she "arranges drugs for a close circle of friends".
The undercover reporter was forced to deny accusations from Contostavlos's barrister Jeremy Dein QC that he entrapped celebrities, bent the truth and invented sources to create "big-time, glamorous stories which enhance your reputation and the paper".
In a series of legal arguments, Mr Dein accused Mr Mahmood of having a "long and chequered history" and of "inventing informers and for creating factual scenarios which are not true".
He said the journalist "tricked and deceived" Contostavlos by wining and dining her at five star hotels and luxury restaurants in a "campaign of entrapment".
To support his case he called former tipster and Kosovan asylum seeker Florim Gashi, who claims to have made up a string of stories with Mr Mahmood at the now defunct News of the World.
Mr Gashi told the court: "Everything was pre-planned from Maz and basically I was involved in assisting him, helping him make up stories for his newspaper."
He said a front-page story in the News of the World in 2002 in which Mr Mahmood claimed to have exposed a plot to kidnap ex-Spice Girl Victoria Beckham and hold her ransom for £5 million, was a set-up.
Five men were arrested but later cleared when the prosecution case collapsed after it was revealed Mr Gashi had been paid £10,000 for the story despite having criminal convictions to his name, and was therefore deemed an unreliable witness.
Questioned about the story, Mr Gashi told the court: "There was nothing genuine in regards to kidnapping Victoria Beckham. This plan originated from Mazher Mahmood and I assisted him to my best to make this story happen."
He accused Mr Mahmood of throwing away tape recordings if they contradicted a story and luring people into committing crimes.
But giving evidence behind a screen to protect his identity, Mr Mahmood vehemently denied the claims and insisted he always took legal advice.
He said: "The information was that she supplies drugs to her friends. She supplied drugs to me - simple."