Four detectives accused of being part of a Flying Squad ring which siphoned off thousands of pounds in stolen cash, were acquitted at the Old Bailey on Friday.
The chief prosecution witness was too ill to attend the Old Bailey
Their prosecution had followed Britain's biggest ever investigation into police corruption.
The officers were cleared after another former policeman who turned "supergrass" failed to give evidence against them.
Detective Constable Kevin Garner had already blown the whistle on other former colleagues who had worked at Rigg Approach in Walthamstow, north east
But Jonathan Laidlaw, who led the prosecution, said Mr Garner was "in no fit state" to come to court because of the stress of six years of being a "supergrass".
The former officers - Detective Sergeant Eamonn Harris, 47,
Detective Sergeant Michael Carroll, 47, Detective Constable David Thompson, 38, and Detective Constable Ian Saunders, 46, - were alleged to have taken £35,000 after catching a gang which had stolen more than £1m.
Their legal representatives said they had always protested, and continued to protest, their innocence.
Mr Garner had helped jail other fellow officers in recent years.
He was jailed himself for six years after admitting a variety of offences
between 1991 and 1996.
It is clear the pressures over the last six years have taken their toll. In his words, Mr Garner cannot cope any longer
He then provided information to the police about alleged corrupt activities by former colleagues.
After the prosecution said there was no realistic chance of Mr Garner being fit to give evidence, Judge Gregory Stone entered verdicts of not guilty to charges of conspiracy to steal, handling stolen goods and perverting justice against the four defendants.
The men shook hands in the dock after being formally cleared.
Mr Laidlaw said the decision not to proceed with the prosecution had been taken "at the highest level of the Crown Prosecution Service and the Metropolitan Police".
Asked by the judge if the option of bringing Mr Garner to court had been considered, Mr Laidlaw said: "He is in no fit state.
"It would do further damage to someone already in an unfit state."
Some five-and-a-half years had elapsed since the four defendants were charged.
Mr Laidlaw said that during the May trial, it had emerged that Mr Garner was suffering from severe psychological and psychiatric difficulties.
"It is clear the pressures over the last six years have taken their toll."
The court was told Mr Garner had been ostracised as an informer, segregated in prison and was now in the Witness Protection Scheme with a new identity.
"He is finding it difficult to integrate himself," said Mr Laidlaw. "In his
words, he cannot cope any longer.
"He falls into the category of a supergrass witness."
Two officers reinstated
Mr Laidlaw said there was little chance of a realistic prospect of conviction without Mr Garner's evidence.
All four men had been suspended from the police force on full pay.
Harris, who was jailed for seven years during a previous trial, was
automatically dismissed on conviction and is still serving his sentence.
A Met Police spokesman said Mr Thompson and Mr Saunders would be reinstated although
no decisions had been taken as to where they would serve.
Mr Carroll would remain suspended pending the decision of a disciplinary panel.