The government has been ordered to make public documents revealing discussions which the then Prime Minister Margaret Thatcher held about the 1989 Hillsborough stadium disaster, where 96 Liverpool fans were killed and for which the police were later blamed.
The Information Commissioner has now ruled that releasing the files would be in the public interest.
His judgment states that the "specific content of the information in question would add to public knowledge and understanding about the reaction of various parties to that event, including the Government of the day, in the early aftermath".
'Unjustified and excessive'
This is in response to a freedom of information application made by the BBC over two years ago. The Commissioner also strongly criticised the Cabinet Office for its "unjustified and excessive" delays in handling the BBC's request.
The Liverpool supporters were killed in an appalling crush of fans within the Hillsborough stadium in Sheffield, where the club was playing an FA Cup semi final. A subsequent inquiry held that the main reason for the overcrowding was the failure of police control.
Mrs Thatcher was briefed about the disaster in the days that followed it, and it was discussed at a number of meetings. The records to be disclosed include reports presented to her, correspondence between her office and that of the Home Secretary Douglas Hurd, and minutes of meetings she attended.
Some campaigners for the families of the victims have suggested that Mrs Thatcher sought to avoid the police being criticised.
The meetings involved include a cabinet meeting. It is unusual for the Commissioner to order the disclosure of cabinet minutes, due to the need to protect the convention of collective responsibility.
The Commissioner argued that due to the reduction of the 30 year rule "there is a diminishing case for withholding information over 20 years old". Gordon Brown as prime minister pledged to reduce the existing 30 year period for making many state documents public, and the coalition government is starting to implement this plan.
In December 2009 the Labour government also set up an independent panel to review the documentation about the Hillsborough tragedy to assess what should now be made public. The Cabinet Office maintained that no material should be disclosed before the panel finishes its work, planned for next year. But the Commissioner discarded this as an irrelevant argument, since the panel had not existed at the time in April 2009 when the BBC's request was made.
The government now has to release the documents or appeal to a tribunal.
The Cabinet Office was recently compelled by the Information Commissioner, Chris Graham, to sign an undertaking to improve the way it handles FOI requests. Mr Graham took action against it because of the frequent severe delays in the Cabinet Office's handling of FOI applications.