During his career, Mazher Mahmood worked at the News of the World, The Sunday Times and latterly The Sun on Sunday, with figures from celebrities to royals caught up in his high-profile exposes.
Known to his colleagues as Maz, the undercover reporter claims to have helped in the convictions of 100 criminals.
The day after the collapse of the Tulisa trial at Southwark Crown Court, Mahmood was suspended by News UK.
In the following months, live trials in which Mahmood was to be a star witness were dropped, while prosecutors looked again at past convictions during the reporter's 25-year career as “King of the Sting”.
In December 2014, the Crown Prosecution Service said it was reviewing 25 convictions and had offered no evidence in three live cases for which Mahmood was to be a prosecution witness.
That year, a judge dropped the case of PR man Leon “Starino” Anderson for allegedly supplying drugs to Mahmood.
Mr Anderson was arrested after The Sun published a story claiming he dealt £300 worth of cocaine and MDMA during what was a dry run for the Tulisa sting.
Judge Alistair McCreath, who also threw out Miss Contostavlos's trial, dismissed the case after prosecutors said Mahmood was not reliable.
The Crown offered no evidence in the case of Dr Majeed Ridha and pharmacist Murtaza Gulamhusein, who were accused of illegally supplying an abortion drug during an undercover investigation for The Sunday Times.
In January last year, prosecutors dropped the case against 13 footballers investigated over alleged match-fixing.
The CPS said there was “insufficient evidence to provide a realistic prospect of conviction” in light of what happened in the Tulisa trial.
The Criminal Cases Review Commission (CCRC) has confirmed it is reviewing six cases involving celebrities who were convicted following involvement with Mahmood, including London's Burning actor John Shannon, aka John Alford.
The actor fell foul to a similar cocaine string as Miss Contostavlos at the Savoy Hotel and was found guilty following a trial at Snaresbrook Crown Court despite insisting he was set up, shattering his budding career.
Others being reviewed by CCRC include the drugs case of Joseph, Earl of Hardwicke, and his business partner Stefan Thwaites; the Pakistan spot-fixing case of businessman Mazhar Majeed; and that of Rani and Joginder Kashyap, who were convicted of an immigration offence.
The application to review the Kashyap's couple case began before the collapse of of the Tulisa trial, while the rest followed the 2014 trial.
A spokesman for the commission said it was “aware of the recent proceedings against Mr Mahmood and we will be thinking carefully about what implications, if any, they may have for those cases involving the Fake Sheikh that we are currently considering”.
The CCRC dealt with a successful appeal involving the Fake Sheikh long before the drugs trial of Miss Contostavlos in July 2014.
In 2010, it referred for appeal the case of Albanian former special forces soldier Besnik Qema, who was convicted for supplying cocaine and for possession of a false passport following a “sting” operation organised by Mahmood.
The appeal that resulted from the commission's referral was uncontested by the Crown.
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