A £6 million murder trial was halted at the Old Bailey today following a Law Lords ruling on witnesses giving evidence anonymously.
The murder trial of two men accused of shooting east London businessman Charles Butler was stopped after lawyers considered last week's ruling.
The Law Lords, in allowing an appeal in another murder case, ruled that defendants have the right to know who is giving evidence against them.
The Old Bailey case is the first casualty of the ruling but dozens of cases around the country are being affected.
The police, the Crown Prosecution Service and defence teams are studying the ruling and reviewing cases.
Judge David Paget discharged the jury at the Old Bailey today after two months of hearing evidence.
The trial, which was nearing the end of the prosecution case, was the culmination of a multimillion-pound four-year inquiry into the shooting and alleged police corruption.
Four witnesses had given evidence under false names and from behind screens.
Prosecutor Timothy Cray said a retrial was expected to be held next year after the ramifications of the ruling had ended.
In an ironic twist, Judge Paget was also the judge in the case of Iain Davis in 2004 which was successfully appealed.
He said it now appeared that defendants not only had the right to know who witnesses were, but also to be able to confront them in court.
Among trials which resulted in convictions recently after witnesses were offered anonymity were the shootings of schoolboy Michael Dosunmu, care worker Magda Pniewska and youth worker Nathan Foster.
Detectives from the Trident squad had boasted of their continuing success rate in tackling gun crime.
Witnesses were urged to come forward, assured that they would be protected with false names, screens and voice distortion.
But the Law Lords ruled that allowing anonymous witnesses in the Davis trial was against British justice.
He had been accused of shooting two people with one bullet which went through a wall at a New Year's party in Hackney, east London, in 2002.
Metropolitan Police Assistant Commissioner John Yates said at the weekend that the ruling was a cause for "grave concern".
He called for the Government to step in with emergency legislation.