Mazher Mahmood, the 'Fake Sheikh', has been jailed for tampering with evidence in the collapsed drugs trial of pop star Tulisa Contostavlos.

Following a two-week trial at the Old Bailey, a jury found the 53-year-old “King of the Sting” and his driver Alan Smith, 67, guilty of plotting to pervert the course of justice.

Judge Gerald Gordon jailed Mahmood for 15 months, saying that while he accepted he had done “some good work” in his long career, there could be no justification for what he had done and custody was inevitable.

He handed Smith 12 months suspended for two years, saying he had been motivated in part by “misguided loyalty”.

As Mahmood was jailed, someone in the public gallery shouted “your turn now Mazher” to the journalist, who claims to have helped in the convictions of 100 criminals during his 25 years of investigative reporting.

Following the guilty verdicts last month, it was announced that 18 civil claims were being launched against Mahmood, which could total some £800 million.

The Crown Prosecution Service has already dropped a number of live cases and reviewed 25 past convictions.

Six of those involving mainly high-profile individuals have been taken up by the Criminal Cases Review Commission.

Judge Gordon told the pair: “You have been convicted by the jury of conspiring to pervert the course of justice.

“You, Alan Smith, agreed to and did alter your original witness statement to remove the passage that you both realised could be used to support Tulisa Contostavlos's case in an entrapment hearing.

“Mazher Mahmood, it was your idea. You were the intended beneficiary and you made use of a loyal person, partly an employee, in order to achieve your purpose.

“The motive was to preserve and enhance your reputation. You wanted another scalp and Miss Contostavlos's conviction would have achieved that.

“To achieve that, when you saw a problem, you were prepared for the court to be deceived.”

He told the journalist that perverting the course of justice in a criminal case was particularly serious as it “undermines the whole process”.

He went on: “Mazher Mahmood, because of your primary role in these proceedings, you were, in my view, in a position of considerable responsibility towards that court and that makes yours a bad example of the offence.”

Judge Gordon acknowledged a letter from the editor of the Sun on Sunday on Mahmood's behalf as well as one from the defendant's mother's GP.

Mahmood's lawyer, John Kelsey-Fry QC, had said his client stood before the court as a “very frightened man”.

Mahmood had been a journalist since his teenage years and his career had not just been characterised by entertainment, the lawyer said in mitigation.

Of the divorced father-of-one, Mr Kelsey-Fry said: “Whatever people say of him today, that career has provided some valuable service.

“By reason of the verdict of the jury, that career is over.

“He has brought catastrophe upon himself and a lifetime's work will be forever tarnished.”

Mr Kelsey-Fry said spending time in prison would be harder for Mahmood than most.

Following the sentence, some of Mahmood's alleged sting victims gathered outside the Old Bailey to call on Parliament to “cleanse this stain on our democracy once and for all”.

Former London's Burning star John Alford, whose case is among those being taken up by the Criminal Cases Review Commission, said: “It’s taken over 20 years for some of us, but finally a judge and a jury of our peers has woken up to Mazher Mahmood’s lies.

“We would now like to ask Parliament to honour their promise to the British people and implement Leveson part two.

“Our three estates, the monarch, our Parliament and our judicial system, must be held accountable, yes?

“But they must not be held to ransom by a corrupt or unscrupulous press. So please let's cleanse this stain on our democracy once and for all.”