Two drug barons who were spared lengthy jail terms by posing as supergrasses, have been jailed for perverting the course of justice.
John Haase, 59, and Paul Bennett, 44, had tipped off police about 150 guns hidden around the UK.
But some detectives started to doubt the authenticity of the information.
At Southwark Crown Court Haase was jailed for 22 years and Bennett for 20 after they were convicted of conspiracy to pervert the course of justice.
Both men were originally jailed for 18 years in 1995 for smuggling heroin but they were freed early after the trial judge alerted the authorities to the help they had given in uncovering arms hidden around the UK.
Their "unique" co-operation, tipping of the authorities about guns, resulted in royal pardons and early freedom.
They were released in 1996 after the then-Home Secretary Michael Howard signed a Royal Prerogative of Mercy.
Haase's wife, Deborah, 37, of Knowsley, Merseyside, whose fingerprints were found on a black bin bag in one of the seizures, was also found guilty of the main charge in addition to possessing firearms and ammunition.
A second woman, Sharon Knowles, 36, of Wadeson Road, Merseyside, was also linked to two of the finds and found guilty of taking part in the plot which the judge described as a "deliberate plan to deceive the courts".
Mr Justice Cooke told them: "You have all been convicted of conspiring to pervert the course of justice in a unique and sophisticated way.
It is a very serious offence. It strikes at the basis of our whole system of justice in this country by seeking to subvert it."
The court heard how Mr Haase provided "leads" about guns which had in fact been planted at the request of him and Mr Bennett.
Paul Bennett was jailed for 20 years
In 1993, while on remand awaiting sentencing in connection with a large consignment of heroin, Haase and Bennett came up with the plan.
But Mr Haase told the court he had paid friends on the outside for information they gleaned from the underworld about guns, drugs, and other criminality.
During the six-week trial there was also a claim that Mr Howard was paid a £400,000 bribe to push the "early release" plot.
Peter Kilfoyle, Labour MP for Liverpool Walton, gave evidence during the trial and said Haase told him about the payment when he visited him in jail.
Mr Kilfoyle told the court he visited Haase in Whitemoor Prison in Cambridgeshire in 2004, when the defendant made a sworn affidavit admitting that accomplices planted guns across Merseyside and the North West of England.
Police had doubts about the authenticity of their "finds", which included an array of 150 handguns, rifles and machine guns.
Fearing the pair would be assassinated by underworld figures for their betrayal, the then judge at Liverpool Crown Court jailed them for 18 years but later wrote to Mr Howard recommending that their sentences be cut.
Haase and Bennett were released after 11 months .
Speaking after the case, Mr Kilfoyle called for an independent inquiry into the affair.
He said there were "huge lessons which need to be drawn from this about how we treat informants and how the courts handle the information from them".
Detective Superintendent Graham McNulty, who led the four-year investigation, said Haase had displayed "a high degree of sophistication and a cunning nature".
He said it was a "virtually unique case" and that the informant system had changed considerably in the years following Haase's first conviction.
But this time the jury took just five hours to unanimously convicted them of conspiring to pervert the course of justice.
They fooled the police into thinking they had become supergrasses
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