The British government has been ordered to publish records of crucial cabinet meetings from 2003, held over the legality of invading Iraq.
"This is an exceptional case," reads the Tuesday verdict of the UK's Information Tribunal -- which decides on requests for documents under freedom of information laws.
According to the decision, it is in the public interest to release minutes of the cabinet meetings from March 13 and 17, 2003, when ministers held talks about whether the decision to go to war was allowed under international law.
"The decision to commit the nation's armed forces to the invasion of another country is momentous in its own right, and... its seriousness is increased by the criticisms that have been made of the general decision-making processes in the Cabinet at the time," the tribunal said.
The Cabinet Office has been fighting for nearly two years to keep the notes secret. It has 28 days to appeal against the decision.
Prime Minister Gordon Brown's Downing Street office announced that it is currently considering its response to the ruling.
The publication of the documents could embarrass Brown, whose predecessor Tony Blair was widely criticized for backing former US president George W. Bush in invading Iraq, despite failing to secure a second United Nations resolution on the war.
The documents are also expected to reveal whether ministers were aware of an apparent change of mind, made by the government's then attorney-general, Peter Goldsmith, on the legality of war.
Previously released documents have shown that Goldsmith had cast doubt on the legal grounds of war on March 7, twelve days before Blair ordered British troops to move into Iraq.
Ten days later, when Britain had failed to secure a second UN resolution authorizing an invasion, Goldsmith gave the cabinet and parliament short written advice that the war was a legal one, according to international law -- even without a UN Security Council ruling.
While Blair denies that Goldsmith had bowed under political pressure, opposition parties accuse the then prime minister of deceit.
Both the Liberal Democrats and the main opposition Conservatives have called for a full inquiry into the US-led invasion of Iraq.