For the third time in as many weeks, the court ruled that the Government had acted unlawfully or unreasonably, twice placing Michael Howard, the Home Secretary, in the judicial firing line.
Earlier this month the Court of Appeal ruled that Mr Howard had abused his powers over his new, cheaper scheme to compensate victims of violent crime. The next day the High Court judged that Douglas Hurd, the Foreign Secretary, acted unlawfully in authorising pounds 234m aid for the Pergau Dam project.
Yesterday's ruling centred upon six men who allege they are the victims of miscarriages of justice, but who claim their chance of proving their innocence had been hampered by the Home Secretary's refusal to disclose evidence - some of it in their favour.
Ordering Mr Howard to hand over evidence in all the cases - which include the three men convicted of the 1978 murder of Carl Bridgewater, the 13-year-old newspaper boy - Lord Justice Simon Brown condemned the present system as ''significantly too closed''.
Paving the way for hundreds of others to access confidential police and Home Office files he said: ''I have no doubt that fairness requires not merely prior disclosure but a substantial increase in the level of disclosures made.''
In the case of Sammy Davis, convicted of rape, the judges said the decisions of previous Home Secretaries - Kenneth Baker and Kenneth Clarke - not to refer his case to the Appeal Court were ''irrational''. They ordered Mr Howard to re-examine the case.
The other two cases were those of Jeremy Bamber, 32, convicted in 1986 of the murders of his adoptive parents, his step-sister and her twins, and Paul Malone, 49, jailed in 1986 for armed robberies.
Mr Howard is considering appealling to the House of Lords, but the Law Lords have already indicated their desire for more open justice in other cases, including the Home Secretary's role in releasing life-sentence prisoners.
Yesterday's judgment increased pressure on the Government to speed up plans for a new independent body to review miscarriages, recommended by the Royal Commission three years ago but not outlined until this month.
Yesterday, defence lawyers, who have condemned the secrecy in the system and the quasi-judicial role of the executive, hoped the judgment would provide a starting point for the new body.
Jim Nichol, representing the Bridgewater Four, said: ''It's a tremendous decision. It blows a great big hole in the secrecy surrounding the way the Home Secretary operates. I have always said the Bridgewater case would come back and haunt Mr Howard . . . there will be a few red faces at the Home Office when it is realised what evidence he has been sitting on.''
Jack Straw, shadow Home Secretary, said the decision was further evidence of the breakdown in the system for dealing with allegations of miscarriages. Alan Beith, Liberal Democrat home affairs spokesman, said: ''Leaving decisions like this to the Home Office never gets things done.''
Background, page 4
Law Report, page 9
Leading article, page 15